Class: Polars::Expr

Inherits:
Object
  • Object
show all
Defined in:
lib/polars/expr.rb

Overview

Expressions that can be used in various contexts.

Instance Method Summary collapse

Instance Method Details

#! ⇒ Expr

Performs boolean not.

Returns:



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# File 'lib/polars/expr.rb', line 134

def !
  is_not
end

#!=(other) ⇒ Expr

Not equal.

Returns:



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# File 'lib/polars/expr.rb', line 113

def !=(other)
  _from_rbexpr(_rbexpr.neq(_to_expr(other)._rbexpr))
end

#%(other) ⇒ Expr

Returns the modulo.

Returns:



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# File 'lib/polars/expr.rb', line 77

def %(other)
  _from_rbexpr(_rbexpr % _to_rbexpr(other))
end

#&(other) ⇒ Expr

Bitwise AND.

Returns:



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# File 'lib/polars/expr.rb', line 35

def &(other)
  _from_rbexpr(_rbexpr._and(_to_rbexpr(other)))
end

#*(other) ⇒ Expr

Performs multiplication.

Returns:



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# File 'lib/polars/expr.rb', line 63

def *(other)
  _from_rbexpr(_rbexpr * _to_rbexpr(other))
end

#**(power) ⇒ Expr

Raises to the power of exponent.

Returns:



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# File 'lib/polars/expr.rb', line 84

def **(power)
  exponent = Utils.parse_into_expression(power)
  _from_rbexpr(_rbexpr.pow(exponent))
end

#+(other) ⇒ Expr

Performs addition.

Returns:



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# File 'lib/polars/expr.rb', line 49

def +(other)
  _from_rbexpr(_rbexpr + _to_rbexpr(other))
end

#-(other) ⇒ Expr

Performs subtraction.

Returns:



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# File 'lib/polars/expr.rb', line 56

def -(other)
  _from_rbexpr(_rbexpr - _to_rbexpr(other))
end

#-@ ⇒ Expr

Performs negation.

Returns:



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# File 'lib/polars/expr.rb', line 141

def -@
  _from_rbexpr(_rbexpr.neg)
end

#/(other) ⇒ Expr

Performs division.

Returns:



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# File 'lib/polars/expr.rb', line 70

def /(other)
  _from_rbexpr(_rbexpr / _to_rbexpr(other))
end

#<(other) ⇒ Expr

Less than.

Returns:



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# File 'lib/polars/expr.rb', line 120

def <(other)
  _from_rbexpr(_rbexpr.lt(_to_expr(other)._rbexpr))
end

#<=(other) ⇒ Expr

Less than or equal.

Returns:



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# File 'lib/polars/expr.rb', line 99

def <=(other)
  _from_rbexpr(_rbexpr.lt_eq(_to_expr(other)._rbexpr))
end

#==(other) ⇒ Expr

Equal.

Returns:



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# File 'lib/polars/expr.rb', line 106

def ==(other)
  _from_rbexpr(_rbexpr.eq(_to_expr(other)._rbexpr))
end

#>(other) ⇒ Expr

Greater than.

Returns:



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# File 'lib/polars/expr.rb', line 127

def >(other)
  _from_rbexpr(_rbexpr.gt(_to_expr(other)._rbexpr))
end

#>=(other) ⇒ Expr

Greater than or equal.

Returns:



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# File 'lib/polars/expr.rb', line 92

def >=(other)
  _from_rbexpr(_rbexpr.gt_eq(_to_expr(other)._rbexpr))
end

#^(other) ⇒ Expr

Bitwise XOR.

Returns:



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# File 'lib/polars/expr.rb', line 28

def ^(other)
  _from_rbexpr(_rbexpr._xor(_to_rbexpr(other)))
end

#_hash(seed = 0, seed_1 = nil, seed_2 = nil, seed_3 = nil) ⇒ Expr

Hash the elements in the selection.

The hash value is of type :u64.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, nil],
    "b" => ["x", nil, "z"]
  }
)
df.with_column(Polars.all._hash(10, 20, 30, 40))
# =>
# shape: (3, 2)
# ┌──────────────────────┬──────────────────────┐
# │ a                    ┆ b                    │
# │ ---                  ┆ ---                  │
# │ u64                  ┆ u64                  │
# ╞══════════════════════╪══════════════════════╡
# │ 4629889412789719550  ┆ 6959506404929392568  │
# │ 16386608652769605760 ┆ 11638928888656214026 │
# │ 11638928888656214026 ┆ 11040941213715918520 │
# └──────────────────────┴──────────────────────┘

Parameters:

  • seed (Integer) (defaults to: 0) —

    Random seed parameter. Defaults to 0.

  • seed_1 (Integer) (defaults to: nil) —

    Random seed parameter. Defaults to seed if not set.

  • seed_2 (Integer) (defaults to: nil) —

    Random seed parameter. Defaults to seed if not set.

  • seed_3 (Integer) (defaults to: nil) —

    Random seed parameter. Defaults to seed if not set.

Returns:



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# File 'lib/polars/expr.rb', line 3892

def _hash(seed = 0, seed_1 = nil, seed_2 = nil, seed_3 = nil)
  k0 = seed
  k1 = seed_1.nil? ? seed : seed_1
  k2 = seed_2.nil? ? seed : seed_2
  k3 = seed_3.nil? ? seed : seed_3
  _from_rbexpr(_rbexpr._hash(k0, k1, k2, k3))
end

#abs ⇒ Expr

Compute absolute values.

Examples:

df = Polars::DataFrame.new(
  {
    "A" => [-1.0, 0.0, 1.0, 2.0]
  }
)
df.select(Polars.col("A").abs)
# =>
# shape: (4, 1)
# ┌─────┐
# │ A   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 1.0 │
# │ 0.0 │
# │ 1.0 │
# │ 2.0 │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 5732

def abs
  _from_rbexpr(_rbexpr.abs)
end

#add(other) ⇒ Expr

Method equivalent of addition operator expr + other.

Examples:

df = Polars::DataFrame.new({"x" => [1, 2, 3, 4, 5]})
df.with_columns(
  Polars.col("x").add(2).alias("x+int"),
  Polars.col("x").add(Polars.col("x").cum_prod).alias("x+expr")
)
# =>
# shape: (5, 3)
# ┌─────┬───────┬────────┐
# │ x   ┆ x+int ┆ x+expr │
# │ --- ┆ ---   ┆ ---    │
# │ i64 ┆ i64   ┆ i64    │
# ╞═════╪═══════╪════════╡
# │ 1   ┆ 3     ┆ 2      │
# │ 2   ┆ 4     ┆ 4      │
# │ 3   ┆ 5     ┆ 9      │
# │ 4   ┆ 6     ┆ 28     │
# │ 5   ┆ 7     ┆ 125    │
# └─────┴───────┴────────┘
df = Polars::DataFrame.new(
  {"x" => ["a", "d", "g"], "y": ["b", "e", "h"], "z": ["c", "f", "i"]}
)
df.with_columns(Polars.col("x").add(Polars.col("y")).add(Polars.col("z")).alias("xyz"))
# =>
# shape: (3, 4)
# ┌─────┬─────┬─────┬─────┐
# │ x   ┆ y   ┆ z   ┆ xyz │
# │ --- ┆ --- ┆ --- ┆ --- │
# │ str ┆ str ┆ str ┆ str │
# ╞═════╪═════╪═════╪═════╡
# │ a   ┆ b   ┆ c   ┆ abc │
# │ d   ┆ e   ┆ f   ┆ def │
# │ g   ┆ h   ┆ i   ┆ ghi │
# └─────┴─────┴─────┴─────┘

Parameters:

  • other (Object) —

    numeric or string value; accepts expression input.

Returns:



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# File 'lib/polars/expr.rb', line 3481

def add(other)
  self + other
end

#agg_groups ⇒ Expr

Get the group indexes of the group by operation.

Should be used in aggregation context only.

Examples:

df = Polars::DataFrame.new(
  {
    "group" => [
      "one",
      "one",
      "one",
      "two",
      "two",
      "two"
    ],
    "value" => [94, 95, 96, 97, 97, 99]
  }
)
df.group_by("group", maintain_order: true).agg(Polars.col("value").agg_groups)
# =>
# shape: (2, 2)
# ┌───────┬───────────┐
# │ group ┆ value     │
# │ ---   ┆ ---       │
# │ str   ┆ list[u32] │
# ╞═══════╪═══════════╡
# │ one   ┆ [0, 1, 2] │
# │ two   ┆ [3, 4, 5] │
# └───────┴───────────┘

Returns:



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# File 'lib/polars/expr.rb', line 741

def agg_groups
  _from_rbexpr(_rbexpr.agg_groups)
end

#alias(name) ⇒ Expr

Rename the output of an expression.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, 3],
    "b" => ["a", "b", nil]
  }
)
df.select(
  [
    Polars.col("a").alias("bar"),
    Polars.col("b").alias("foo")
  ]
)
# =>
# shape: (3, 2)
# ┌─────┬──────┐
# │ bar ┆ foo  │
# │ --- ┆ ---  │
# │ i64 ┆ str  │
# ╞═════╪══════╡
# │ 1   ┆ a    │
# │ 2   ┆ b    │
# │ 3   ┆ null │
# └─────┴──────┘

Parameters:

Returns:



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# File 'lib/polars/expr.rb', line 324

def alias(name)
  _from_rbexpr(_rbexpr._alias(name))
end

#all(drop_nulls: true) ⇒ Boolean

Check if all boolean values in a Boolean column are true.

This method is an expression - not to be confused with Polars.all which is a function to select all columns.

Examples:

df = Polars::DataFrame.new(
  {"TT" => [true, true], "TF" => [true, false], "FF" => [false, false]}
)
df.select(Polars.col("*").all)
# =>
# shape: (1, 3)
# ┌──────┬───────┬───────┐
# │ TT   ┆ TF    ┆ FF    │
# │ ---  ┆ ---   ┆ ---   │
# │ bool ┆ bool  ┆ bool  │
# ╞══════╪═══════╪═══════╡
# │ true ┆ false ┆ false │
# └──────┴───────┴───────┘

Returns:



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# File 'lib/polars/expr.rb', line 223

def all(drop_nulls: true)
  _from_rbexpr(_rbexpr.all(drop_nulls))
end

#any(drop_nulls: true) ⇒ Boolean

Check if any boolean value in a Boolean column is true.

Examples:

df = Polars::DataFrame.new({"TF" => [true, false], "FF" => [false, false]})
df.select(Polars.all.any)
# =>
# shape: (1, 2)
# ┌──────┬───────┐
# │ TF   ┆ FF    │
# │ ---  ┆ ---   │
# │ bool ┆ bool  │
# ╞══════╪═══════╡
# │ true ┆ false │
# └──────┴───────┘

Returns:



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# File 'lib/polars/expr.rb', line 198

def any(drop_nulls: true)
  _from_rbexpr(_rbexpr.any(drop_nulls))
end

#append(other, upcast: true) ⇒ Expr

Append expressions.

This is done by adding the chunks of other to this Series.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [8, 9, 10],
    "b" => [nil, 4, 4]
  }
)
df.select(Polars.all.head(1).append(Polars.all.tail(1)))
# =>
# shape: (2, 2)
# ┌─────┬──────┐
# │ a   ┆ b    │
# │ --- ┆ ---  │
# │ i64 ┆ i64  │
# ╞═════╪══════╡
# │ 8   ┆ null │
# │ 10  ┆ 4    │
# └─────┴──────┘

Parameters:

  • other (Expr) —

    Expression to append.

  • upcast (Boolean) (defaults to: true) —

    Cast both Series to the same supertype.

Returns:



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# File 'lib/polars/expr.rb', line 853

def append(other, upcast: true)
  other = Utils.parse_into_expression(other)
  _from_rbexpr(_rbexpr.append(other, upcast))
end

#approx_n_unique ⇒ Expr Also known as: approx_unique

Approx count unique values.

This is done using the HyperLogLog++ algorithm for cardinality estimation.

Examples:

df = Polars::DataFrame.new({"a" => [1, 1, 2]})
df.select(Polars.col("a").approx_n_unique)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ u32 │
# ╞═════╡
# │ 2   │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2187

def approx_n_unique
  _from_rbexpr(_rbexpr.approx_n_unique)
end

#arccos ⇒ Expr

Compute the element-wise value for the inverse cosine.

Examples:

df = Polars::DataFrame.new({"a" => [0.0]})
df.select(Polars.col("a").arccos)
# =>
# shape: (1, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 1.570796 │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6227

def arccos
  _from_rbexpr(_rbexpr.arccos)
end

#arccosh ⇒ Expr

Compute the element-wise value for the inverse hyperbolic cosine.

Examples:

df = Polars::DataFrame.new({"a" => [1.0]})
df.select(Polars.col("a").arccosh)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 0.0 │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 6347

def arccosh
  _from_rbexpr(_rbexpr.arccosh)
end

#arcsin ⇒ Expr

Compute the element-wise value for the inverse sine.

Examples:

df = Polars::DataFrame.new({"a" => [1.0]})
df.select(Polars.col("a").arcsin)
# =>
# shape: (1, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 1.570796 │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6207

def arcsin
  _from_rbexpr(_rbexpr.arcsin)
end

#arcsinh ⇒ Expr

Compute the element-wise value for the inverse hyperbolic sine.

Examples:

df = Polars::DataFrame.new({"a" => [1.0]})
df.select(Polars.col("a").arcsinh)
# =>
# shape: (1, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 0.881374 │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6327

def arcsinh
  _from_rbexpr(_rbexpr.arcsinh)
end

#arctan ⇒ Expr

Compute the element-wise value for the inverse tangent.

Examples:

df = Polars::DataFrame.new({"a" => [1.0]})
df.select(Polars.col("a").arctan)
# =>
# shape: (1, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 0.785398 │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6247

def arctan
  _from_rbexpr(_rbexpr.arctan)
end

#arctanh ⇒ Expr

Compute the element-wise value for the inverse hyperbolic tangent.

Examples:

df = Polars::DataFrame.new({"a" => [1.0]})
df.select(Polars.col("a").arctanh)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ inf │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 6367

def arctanh
  _from_rbexpr(_rbexpr.arctanh)
end

#arg_max ⇒ Expr

Get the index of the maximal value.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [20, 10, 30]
  }
)
df.select(Polars.col("a").arg_max)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ u32 │
# ╞═════╡
# │ 2   │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 1483

def arg_max
  _from_rbexpr(_rbexpr.arg_max)
end

#arg_min ⇒ Expr

Get the index of the minimal value.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [20, 10, 30]
  }
)
df.select(Polars.col("a").arg_min)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ u32 │
# ╞═════╡
# │ 1   │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 1507

def arg_min
  _from_rbexpr(_rbexpr.arg_min)
end

#arg_sort(reverse: false, nulls_last: false) ⇒ Expr

Get the index values that would sort this column.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [20, 10, 30]
  }
)
df.select(Polars.col("a").arg_sort)
# =>
# shape: (3, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ u32 │
# ╞═════╡
# │ 1   │
# │ 0   │
# │ 2   │
# └─────┘

Parameters:

  • reverse (Boolean) (defaults to: false) —

    Sort in reverse (descending) order.

  • nulls_last (Boolean) (defaults to: false) —

    Place null values last instead of first.

Returns:



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# File 'lib/polars/expr.rb', line 1459

def arg_sort(reverse: false, nulls_last: false)
  _from_rbexpr(_rbexpr.arg_sort(reverse, nulls_last))
end

#arg_unique ⇒ Expr

Get index of first unique value.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [8, 9, 10],
    "b" => [nil, 4, 4]
  }
)
df.select(Polars.col("a").arg_unique)
# =>
# shape: (3, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ u32 │
# ╞═════╡
# │ 0   │
# │ 1   │
# │ 2   │
# └─────┘
df.select(Polars.col("b").arg_unique)
# =>
# shape: (2, 1)
# ┌─────┐
# │ b   │
# │ --- │
# │ u32 │
# ╞═════╡
# │ 0   │
# │ 1   │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2253

def arg_unique
  _from_rbexpr(_rbexpr.arg_unique)
end

#argsort(reverse: false, nulls_last: false) ⇒ expr

Get the index values that would sort this column.

Alias for #arg_sort.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [20, 10, 30]
  }
)
df.select(Polars.col("a").argsort)
# =>
# shape: (3, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ u32 │
# ╞═════╡
# │ 1   │
# │ 0   │
# │ 2   │
# └─────┘

Parameters:

  • reverse (Boolean) (defaults to: false) —

    Sort in reverse (descending) order.

  • nulls_last (Boolean) (defaults to: false) —

    Place null values last instead of first.

Returns:

  • (expr) 


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# File 'lib/polars/expr.rb', line 5765

def argsort(reverse: false, nulls_last: false)
  arg_sort(reverse: reverse, nulls_last: nulls_last)
end

#arr ⇒ ArrayExpr

Create an object namespace of all array related methods.

Returns:



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# File 'lib/polars/expr.rb', line 7240

def arr
  ArrayExpr.new(self)
end

#backward_fill(limit: nil) ⇒ Expr

Fill missing values with the next to be seen values.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, nil],
    "b" => [4, nil, 6]
  }
)
df.select(Polars.all.backward_fill)
# =>
# shape: (3, 2)
# ┌──────┬─────┐
# │ a    ┆ b   │
# │ ---  ┆ --- │
# │ i64  ┆ i64 │
# ╞══════╪═════╡
# │ 1    ┆ 4   │
# │ 2    ┆ 6   │
# │ null ┆ 6   │
# └──────┴─────┘

Parameters:

  • limit (Integer) (defaults to: nil) —

    The number of consecutive null values to backward fill.

Returns:



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# File 'lib/polars/expr.rb', line 1899

def backward_fill(limit: nil)
  _from_rbexpr(_rbexpr.backward_fill(limit))
end

#bin ⇒ BinaryExpr

Create an object namespace of all binary related methods.

Returns:



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# File 'lib/polars/expr.rb', line 7247

def bin
  BinaryExpr.new(self)
end

#bottom_k(k: 5) ⇒ Expr

Return the k smallest elements.

If 'reverse: true` the smallest elements will be given.

Examples:

df = Polars::DataFrame.new(
  {
    "value" => [1, 98, 2, 3, 99, 4]
  }
)
df.select(
  [
    Polars.col("value").top_k.alias("top_k"),
    Polars.col("value").bottom_k.alias("bottom_k")
  ]
)
# =>
# shape: (5, 2)
# ┌───────┬──────────┐
# │ top_k ┆ bottom_k │
# │ ---   ┆ ---      │
# │ i64   ┆ i64      │
# ╞═══════╪══════════╡
# │ 99    ┆ 1        │
# │ 98    ┆ 2        │
# │ 4     ┆ 3        │
# │ 3     ┆ 4        │
# │ 2     ┆ 98       │
# └───────┴──────────┘

Parameters:

  • k (Integer) (defaults to: 5) —

    Number of elements to return.

Returns:



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# File 'lib/polars/expr.rb', line 1427

def bottom_k(k: 5)
  k = Utils.parse_into_expression(k)
  _from_rbexpr(_rbexpr.bottom_k(k))
end

#cast(dtype, strict: true) ⇒ Expr

Cast between data types.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, 3],
    "b" => ["4", "5", "6"]
  }
)
df.with_columns(
  [
    Polars.col("a").cast(:f64),
    Polars.col("b").cast(:i32)
  ]
)
# =>
# shape: (3, 2)
# ┌─────┬─────┐
# │ a   ┆ b   │
# │ --- ┆ --- │
# │ f64 ┆ i32 │
# ╞═════╪═════╡
# │ 1.0 ┆ 4   │
# │ 2.0 ┆ 5   │
# │ 3.0 ┆ 6   │
# └─────┴─────┘

Parameters:

  • dtype (Symbol) —

    DataType to cast to.

  • strict (Boolean) (defaults to: true) —

    Throw an error if a cast could not be done. For instance, due to an overflow.

Returns:



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# File 'lib/polars/expr.rb', line 1274

def cast(dtype, strict: true)
  dtype = Utils.rb_type_to_dtype(dtype)
  _from_rbexpr(_rbexpr.cast(dtype, strict))
end

#cat ⇒ CatExpr

Create an object namespace of all categorical related methods.

Returns:



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# File 'lib/polars/expr.rb', line 7254

def cat
  CatExpr.new(self)
end

#ceil ⇒ Expr

Rounds up to the nearest integer value.

Only works on floating point Series.

Examples:

df = Polars::DataFrame.new({"a" => [0.3, 0.5, 1.0, 1.1]})
df.select(Polars.col("a").ceil)
# =>
# shape: (4, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 1.0 │
# │ 1.0 │
# │ 1.0 │
# │ 2.0 │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 1153

def ceil
  _from_rbexpr(_rbexpr.ceil)
end

#clip(lower_bound = nil, upper_bound = nil) ⇒ Expr

Set values outside the given boundaries to the boundary value.

Only works for numeric and temporal columns. If you want to clip other data types, consider writing a when-then-otherwise expression.

Examples:

df = Polars::DataFrame.new({"foo" => [-50, 5, nil, 50]})
df.with_column(Polars.col("foo").clip(1, 10).alias("foo_clipped"))
# =>
# shape: (4, 2)
# ┌──────┬─────────────┐
# │ foo  ┆ foo_clipped │
# │ ---  ┆ ---         │
# │ i64  ┆ i64         │
# ╞══════╪═════════════╡
# │ -50  ┆ 1           │
# │ 5    ┆ 5           │
# │ null ┆ null        │
# │ 50   ┆ 10          │
# └──────┴─────────────┘

Parameters:

  • lower_bound (Numeric) (defaults to: nil) —

    Minimum value.

  • upper_bound (Numeric) (defaults to: nil) —

    Maximum value.

Returns:



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# File 'lib/polars/expr.rb', line 5989

def clip(lower_bound = nil, upper_bound = nil)
  if !lower_bound.nil?
    lower_bound = Utils.parse_into_expression(lower_bound)
  end
  if !upper_bound.nil?
    upper_bound = Utils.parse_into_expression(upper_bound)
  end
  _from_rbexpr(_rbexpr.clip(lower_bound, upper_bound))
end

#clip_max(upper_bound) ⇒ Expr

Clip (limit) the values in an array to a max boundary.

Only works for numerical types.

If you want to clip other dtypes, consider writing a "when, then, otherwise" expression. See when for more information.

Examples:

df = Polars::DataFrame.new({"foo" => [-50, 5, nil, 50]})
df.with_column(Polars.col("foo").clip_max(0).alias("foo_clipped"))
# =>
# shape: (4, 2)
# ┌──────┬─────────────┐
# │ foo  ┆ foo_clipped │
# │ ---  ┆ ---         │
# │ i64  ┆ i64         │
# ╞══════╪═════════════╡
# │ -50  ┆ -50         │
# │ 5    ┆ 0           │
# │ null ┆ null        │
# │ 50   ┆ 0           │
# └──────┴─────────────┘

Parameters:

  • upper_bound (Numeric) —

    Maximum value.

Returns:



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# File 'lib/polars/expr.rb', line 6057

def clip_max(upper_bound)
  clip(nil, upper_bound)
end

#clip_min(lower_bound) ⇒ Expr

Clip (limit) the values in an array to a min boundary.

Only works for numerical types.

If you want to clip other dtypes, consider writing a "when, then, otherwise" expression. See when for more information.

Examples:

df = Polars::DataFrame.new({"foo" => [-50, 5, nil, 50]})
df.with_column(Polars.col("foo").clip_min(0).alias("foo_clipped"))
# =>
# shape: (4, 2)
# ┌──────┬─────────────┐
# │ foo  ┆ foo_clipped │
# │ ---  ┆ ---         │
# │ i64  ┆ i64         │
# ╞══════╪═════════════╡
# │ -50  ┆ 0           │
# │ 5    ┆ 5           │
# │ null ┆ null        │
# │ 50   ┆ 50          │
# └──────┴─────────────┘

Parameters:

  • lower_bound (Numeric) —

    Minimum value.

Returns:



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# File 'lib/polars/expr.rb', line 6026

def clip_min(lower_bound)
  clip(lower_bound, nil)
end

#cos ⇒ Expr

Compute the element-wise value for the cosine.

Examples:

df = Polars::DataFrame.new({"a" => [0.0]})
df.select(Polars.col("a").cos)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 1.0 │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 6167

def cos
  _from_rbexpr(_rbexpr.cos)
end

#cosh ⇒ Expr

Compute the element-wise value for the hyperbolic cosine.

Examples:

df = Polars::DataFrame.new({"a" => [1.0]})
df.select(Polars.col("a").cosh)
# =>
# shape: (1, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 1.543081 │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6287

def cosh
  _from_rbexpr(_rbexpr.cosh)
end

#count ⇒ Expr

Count the number of values in this expression.

Examples:

df = Polars::DataFrame.new({"a" => [8, 9, 10], "b" => [nil, 4, 4]})
df.select(Polars.all.count)
# =>
# shape: (1, 2)
# ┌─────┬─────┐
# │ a   ┆ b   │
# │ --- ┆ --- │
# │ u32 ┆ u32 │
# ╞═════╪═════╡
# │ 3   ┆ 2   │
# └─────┴─────┘

Returns:



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# File 'lib/polars/expr.rb', line 761

def count
  _from_rbexpr(_rbexpr.count)
end

#cum_count(reverse: false) ⇒ Expr Also known as: cumcount

Get an array with the cumulative count computed at every element.

Counting from 0 to len

Examples:

df = Polars::DataFrame.new({"a" => ["x", "k", nil, "d"]})
df.with_columns(
  [
    Polars.col("a").cum_count.alias("cum_count"),
    Polars.col("a").cum_count(reverse: true).alias("cum_count_reverse")
  ]
)
# =>
# shape: (4, 3)
# ┌──────┬───────────┬───────────────────┐
# │ a    ┆ cum_count ┆ cum_count_reverse │
# │ ---  ┆ ---       ┆ ---               │
# │ str  ┆ u32       ┆ u32               │
# ╞══════╪═══════════╪═══════════════════╡
# │ x    ┆ 1         ┆ 3                 │
# │ k    ┆ 2         ┆ 2                 │
# │ null ┆ 2         ┆ 1                 │
# │ d    ┆ 3         ┆ 1                 │
# └──────┴───────────┴───────────────────┘

Parameters:

  • reverse (Boolean) (defaults to: false) —

    Reverse the operation.

Returns:



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# File 'lib/polars/expr.rb', line 1102

def cum_count(reverse: false)
  _from_rbexpr(_rbexpr.cum_count(reverse))
end

#cum_max(reverse: false) ⇒ Expr Also known as: cummax

Get an array with the cumulative max computed at every element.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3, 4]})
df.select(
  [
    Polars.col("a").cum_max,
    Polars.col("a").cum_max(reverse: true).alias("a_reverse")
  ]
)
# =>
# shape: (4, 2)
# ┌─────┬───────────┐
# │ a   ┆ a_reverse │
# │ --- ┆ ---       │
# │ i64 ┆ i64       │
# ╞═════╪═══════════╡
# │ 1   ┆ 4         │
# │ 2   ┆ 4         │
# │ 3   ┆ 4         │
# │ 4   ┆ 4         │
# └─────┴───────────┘

Parameters:

  • reverse (Boolean) (defaults to: false) —

    Reverse the operation.

Returns:



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# File 'lib/polars/expr.rb', line 1068

def cum_max(reverse: false)
  _from_rbexpr(_rbexpr.cum_max(reverse))
end

#cum_min(reverse: false) ⇒ Expr Also known as: cummin

Get an array with the cumulative min computed at every element.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3, 4]})
df.select(
  [
    Polars.col("a").cum_min,
    Polars.col("a").cum_min(reverse: true).alias("a_reverse")
  ]
)
# =>
# shape: (4, 2)
# ┌─────┬───────────┐
# │ a   ┆ a_reverse │
# │ --- ┆ ---       │
# │ i64 ┆ i64       │
# ╞═════╪═══════════╡
# │ 1   ┆ 1         │
# │ 1   ┆ 2         │
# │ 1   ┆ 3         │
# │ 1   ┆ 4         │
# └─────┴───────────┘

Parameters:

  • reverse (Boolean) (defaults to: false) —

    Reverse the operation.

Returns:



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# File 'lib/polars/expr.rb', line 1036

def cum_min(reverse: false)
  _from_rbexpr(_rbexpr.cum_min(reverse))
end

#cum_prod(reverse: false) ⇒ Expr Also known as: cumprod

Note:

Dtypes in :i8, :u8, :i16, and :u16 are cast to :i64 before summing to prevent overflow issues.

Get an array with the cumulative product computed at every element.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3, 4]})
df.select(
  [
    Polars.col("a").cum_prod,
    Polars.col("a").cum_prod(reverse: true).alias("a_reverse")
  ]
)
# =>
# shape: (4, 2)
# ┌─────┬───────────┐
# │ a   ┆ a_reverse │
# │ --- ┆ ---       │
# │ i64 ┆ i64       │
# ╞═════╪═══════════╡
# │ 1   ┆ 24        │
# │ 2   ┆ 24        │
# │ 6   ┆ 12        │
# │ 24  ┆ 4         │
# └─────┴───────────┘

Parameters:

  • reverse (Boolean) (defaults to: false) —

    Reverse the operation.

Returns:



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# File 'lib/polars/expr.rb', line 1004

def cum_prod(reverse: false)
  _from_rbexpr(_rbexpr.cum_prod(reverse))
end

#cum_sum(reverse: false) ⇒ Expr Also known as: cumsum

Note:

Dtypes in :i8, :u8, :i16, and :u16 are cast to :i64 before summing to prevent overflow issues.

Get an array with the cumulative sum computed at every element.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3, 4]})
df.select(
  [
    Polars.col("a").cum_sum,
    Polars.col("a").cum_sum(reverse: true).alias("a_reverse")
  ]
)
# =>
# shape: (4, 2)
# ┌─────┬───────────┐
# │ a   ┆ a_reverse │
# │ --- ┆ ---       │
# │ i64 ┆ i64       │
# ╞═════╪═══════════╡
# │ 1   ┆ 10        │
# │ 3   ┆ 9         │
# │ 6   ┆ 7         │
# │ 10  ┆ 4         │
# └─────┴───────────┘

Parameters:

  • reverse (Boolean) (defaults to: false) —

    Reverse the operation.

Returns:



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# File 'lib/polars/expr.rb', line 968

def cum_sum(reverse: false)
  _from_rbexpr(_rbexpr.cum_sum(reverse))
end

#cumulative_eval(expr, min_periods: 1, parallel: false) ⇒ Expr

Note:

This functionality is experimental and may change without it being considered a breaking change.

Note:

This can be really slow as it can have O(n^2) complexity. Don't use this for operations that visit all elements.

Run an expression over a sliding window that increases 1 slot every iteration.

Examples:

df = Polars::DataFrame.new({"values" => [1, 2, 3, 4, 5]})
df.select(
  [
    Polars.col("values").cumulative_eval(
      Polars.element.first - Polars.element.last ** 2
    )
  ]
)
# =>
# shape: (5, 1)
# ┌────────┐
# │ values │
# │ ---    │
# │ i64    │
# ╞════════╡
# │ 0      │
# │ -3     │
# │ -8     │
# │ -15    │
# │ -24    │
# └────────┘

Parameters:

  • expr (Expr) —

    Expression to evaluate

  • min_periods (Integer) (defaults to: 1) —

    Number of valid values there should be in the window before the expression is evaluated. valid values = length - null_count

  • parallel (Boolean) (defaults to: false) —

    Run in parallel. Don't do this in a group by or another operation that already has much parallelization.

Returns:



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# File 'lib/polars/expr.rb', line 6822

def cumulative_eval(expr, min_periods: 1, parallel: false)
  _from_rbexpr(
    _rbexpr.cumulative_eval(expr._rbexpr, min_periods, parallel)
  )
end

#cut(breaks, labels: nil, left_closed: false, include_breaks: false) ⇒ Expr

Bin continuous values into discrete categories.

Examples:

Divide a column into three categories.

df = Polars::DataFrame.new({"foo" => [-2, -1, 0, 1, 2]})
df.with_columns(
  Polars.col("foo").cut([-1, 1], labels: ["a", "b", "c"]).alias("cut")
)
# =>
# shape: (5, 2)
# ┌─────┬─────┐
# │ foo ┆ cut │
# │ --- ┆ --- │
# │ i64 ┆ cat │
# ╞═════╪═════╡
# │ -2  ┆ a   │
# │ -1  ┆ a   │
# │ 0   ┆ b   │
# │ 1   ┆ b   │
# │ 2   ┆ c   │
# └─────┴─────┘

Add both the category and the breakpoint.

df.with_columns(
  Polars.col("foo").cut([-1, 1], include_breaks: true).alias("cut")
).unnest("cut")
# =>
# shape: (5, 3)
# ┌─────┬────────────┬────────────┐
# │ foo ┆ breakpoint ┆ category   │
# │ --- ┆ ---        ┆ ---        │
# │ i64 ┆ f64        ┆ cat        │
# ╞═════╪════════════╪════════════╡
# │ -2  ┆ -1.0       ┆ (-inf, -1] │
# │ -1  ┆ -1.0       ┆ (-inf, -1] │
# │ 0   ┆ 1.0        ┆ (-1, 1]    │
# │ 1   ┆ 1.0        ┆ (-1, 1]    │
# │ 2   ┆ inf        ┆ (1, inf]   │
# └─────┴────────────┴────────────┘

Parameters:

  • breaks (Array) —

    List of unique cut points.

  • labels (Array) (defaults to: nil) —

    Names of the categories. The number of labels must be equal to the number of cut points plus one.

  • left_closed (Boolean) (defaults to: false) —

    Set the intervals to be left-closed instead of right-closed.

  • include_breaks (Boolean) (defaults to: false) —

    Include a column with the right endpoint of the bin each observation falls in. This will change the data type of the output from a Categorical to a Struct.

Returns:



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# File 'lib/polars/expr.rb', line 2636

def cut(breaks, labels: nil, left_closed: false, include_breaks: false)
  _from_rbexpr(_rbexpr.cut(breaks, labels, left_closed, include_breaks))
end

#diff(n: 1, null_behavior: "ignore") ⇒ Expr

Calculate the n-th discrete difference.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [20, 10, 30]
  }
)
df.select(Polars.col("a").diff)
# =>
# shape: (3, 1)
# ┌──────┐
# │ a    │
# │ ---  │
# │ i64  │
# ╞══════╡
# │ null │
# │ -10  │
# │ 20   │
# └──────┘

Parameters:

  • n (Integer) (defaults to: 1) —

    Number of slots to shift.

  • null_behavior ("ignore", "drop") (defaults to: "ignore") —

    How to handle null values.

Returns:



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# File 'lib/polars/expr.rb', line 5860

def diff(n: 1, null_behavior: "ignore")
  _from_rbexpr(_rbexpr.diff(n, null_behavior))
end

#dot(other) ⇒ Expr

Compute the dot/inner product between two Expressions.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 3, 5],
    "b" => [2, 4, 6]
  }
)
df.select(Polars.col("a").dot(Polars.col("b")))
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 44  │
# └─────┘

Parameters:

  • other (Expr) —

    Expression to compute dot product with.

Returns:



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# File 'lib/polars/expr.rb', line 1207

def dot(other)
  other = Utils.parse_into_expression(other, str_as_lit: false)
  _from_rbexpr(_rbexpr.dot(other))
end

#drop_nans ⇒ Expr

Drop floating point NaN values.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [8, 9, 10, 11],
    "b" => [nil, 4.0, 4.0, Float::NAN]
  }
)
df.select(Polars.col("b").drop_nans)
# =>
# shape: (3, 1)
# ┌──────┐
# │ b    │
# │ ---  │
# │ f64  │
# ╞══════╡
# │ null │
# │ 4.0  │
# │ 4.0  │
# └──────┘

Returns:



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# File 'lib/polars/expr.rb', line 933

def drop_nans
  _from_rbexpr(_rbexpr.drop_nans)
end

#drop_nulls ⇒ Expr

Drop null values.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [8, 9, 10, 11],
    "b" => [nil, 4.0, 4.0, Float::NAN]
  }
)
df.select(Polars.col("b").drop_nulls)
# =>
# shape: (3, 1)
# ┌─────┐
# │ b   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 4.0 │
# │ 4.0 │
# │ NaN │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 906

def drop_nulls
  _from_rbexpr(_rbexpr.drop_nulls)
end

#dt ⇒ DateTimeExpr

Create an object namespace of all datetime related methods.

Returns:



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# File 'lib/polars/expr.rb', line 7261

def dt
  DateTimeExpr.new(self)
end

#entropy(base: 2, normalize: true) ⇒ Expr

Computes the entropy.

Uses the formula -sum(pk * log(pk) where pk are discrete probabilities.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3]})
df.select(Polars.col("a").entropy(base: 2))
# =>
# shape: (1, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 1.459148 │
# └──────────┘
df.select(Polars.col("a").entropy(base: 2, normalize: false))
# =>
# shape: (1, 1)
# ┌───────────┐
# │ a         │
# │ ---       │
# │ f64       │
# ╞═══════════╡
# │ -6.754888 │
# └───────────┘

Parameters:

  • base (Float) (defaults to: 2) —

    Given base, defaults to e.

  • normalize (Boolean) (defaults to: true) —

    Normalize pk if it doesn't sum to 1.

Returns:



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# File 'lib/polars/expr.rb', line 6775

def entropy(base: 2, normalize: true)
  _from_rbexpr(_rbexpr.entropy(base, normalize))
end

#eq(other) ⇒ Expr

Method equivalent of equality operator expr == other.

Examples:

df = Polars::DataFrame.new(
  {
    "x" => [1.0, 2.0, Float::NAN, 4.0],
    "y" => [2.0, 2.0, Float::NAN, 4.0]
  }
)
df.with_columns(
  Polars.col("x").eq(Polars.col("y")).alias("x == y")
)
# =>
# shape: (4, 3)
# ┌─────┬─────┬────────┐
# │ x   ┆ y   ┆ x == y │
# │ --- ┆ --- ┆ ---    │
# │ f64 ┆ f64 ┆ bool   │
# ╞═════╪═════╪════════╡
# │ 1.0 ┆ 2.0 ┆ false  │
# │ 2.0 ┆ 2.0 ┆ true   │
# │ NaN ┆ NaN ┆ true   │
# │ 4.0 ┆ 4.0 ┆ true   │
# └─────┴─────┴────────┘

Parameters:

  • other (Object) —

    A literal or expression value to compare with.

Returns:



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# File 'lib/polars/expr.rb', line 3191

def eq(other)
  self == other
end

#eq_missing(other) ⇒ Expr

Method equivalent of equality operator expr == other where None == None.

This differs from default eq where null values are propagated.

Examples:

df = Polars::DataFrame.new(
  data={
    "x" => [1.0, 2.0, Float::NAN, 4.0, nil, nil],
    "y" => [2.0, 2.0, Float::NAN, 4.0, 5.0, nil]
  }
)
df.with_columns(
  Polars.col("x").eq(Polars.col("y")).alias("x eq y"),
  Polars.col("x").eq_missing(Polars.col("y")).alias("x eq_missing y")
)
# =>
# shape: (6, 4)
# ┌──────┬──────┬────────┬────────────────┐
# │ x    ┆ y    ┆ x eq y ┆ x eq_missing y │
# │ ---  ┆ ---  ┆ ---    ┆ ---            │
# │ f64  ┆ f64  ┆ bool   ┆ bool           │
# ╞══════╪══════╪════════╪════════════════╡
# │ 1.0  ┆ 2.0  ┆ false  ┆ false          │
# │ 2.0  ┆ 2.0  ┆ true   ┆ true           │
# │ NaN  ┆ NaN  ┆ true   ┆ true           │
# │ 4.0  ┆ 4.0  ┆ true   ┆ true           │
# │ null ┆ 5.0  ┆ null   ┆ false          │
# │ null ┆ null ┆ null   ┆ true           │
# └──────┴──────┴────────┴────────────────┘

Parameters:

  • other (Object) —

    A literal or expression value to compare with.

Returns:



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# File 'lib/polars/expr.rb', line 3229

def eq_missing(other)
  other = Utils.parse_into_expression(other, str_as_lit: true)
  _from_rbexpr(_rbexpr.eq_missing(other))
end

#ewm_mean(com: nil, span: nil, half_life: nil, alpha: nil, adjust: true, min_periods: 1, ignore_nulls: true) ⇒ Expr

Exponentially-weighted moving average.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3]})
df.select(Polars.col("a").ewm_mean(com: 1))
# =>
# shape: (3, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 1.0      │
# │ 1.666667 │
# │ 2.428571 │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6519

def ewm_mean(
  com: nil,
  span: nil,
  half_life: nil,
  alpha: nil,
  adjust: true,
  min_periods: 1,
  ignore_nulls: true
)
  alpha = _prepare_alpha(com, span, half_life, alpha)
  _from_rbexpr(_rbexpr.ewm_mean(alpha, adjust, min_periods, ignore_nulls))
end

#ewm_std(com: nil, span: nil, half_life: nil, alpha: nil, adjust: true, bias: false, min_periods: 1, ignore_nulls: true) ⇒ Expr

Exponentially-weighted moving standard deviation.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3]})
df.select(Polars.col("a").ewm_std(com: 1))
# =>
# shape: (3, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 0.0      │
# │ 0.707107 │
# │ 0.963624 │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6550

def ewm_std(
  com: nil,
  span: nil,
  half_life: nil,
  alpha: nil,
  adjust: true,
  bias: false,
  min_periods: 1,
  ignore_nulls: true
)
  alpha = _prepare_alpha(com, span, half_life, alpha)
  _from_rbexpr(_rbexpr.ewm_std(alpha, adjust, bias, min_periods, ignore_nulls))
end

#ewm_var(com: nil, span: nil, half_life: nil, alpha: nil, adjust: true, bias: false, min_periods: 1, ignore_nulls: true) ⇒ Expr

Exponentially-weighted moving variance.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3]})
df.select(Polars.col("a").ewm_var(com: 1))
# =>
# shape: (3, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 0.0      │
# │ 0.5      │
# │ 0.928571 │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6582

def ewm_var(
  com: nil,
  span: nil,
  half_life: nil,
  alpha: nil,
  adjust: true,
  bias: false,
  min_periods: 1,
  ignore_nulls: true
)
  alpha = _prepare_alpha(com, span, half_life, alpha)
  _from_rbexpr(_rbexpr.ewm_var(alpha, adjust, bias, min_periods, ignore_nulls))
end

#exclude(columns) ⇒ Expr

Exclude certain columns from a wildcard/regex selection.

You may also use regexes in the exclude list. They must start with ^ and end with $.

Examples:

df = Polars::DataFrame.new(
  {
    "aa" => [1, 2, 3],
    "ba" => ["a", "b", nil],
    "cc" => [nil, 2.5, 1.5]
  }
)
df.select(Polars.all.exclude("ba"))
# =>
# shape: (3, 2)
# ┌─────┬──────┐
# │ aa  ┆ cc   │
# │ --- ┆ ---  │
# │ i64 ┆ f64  │
# ╞═════╪══════╡
# │ 1   ┆ null │
# │ 2   ┆ 2.5  │
# │ 3   ┆ 1.5  │
# └─────┴──────┘

Parameters:

  • columns (Object) —

    Column(s) to exclude from selection. This can be:

    • a column name, or multiple column names
    • a regular expression starting with ^ and ending with $
    • a dtype or multiple dtypes

Returns:



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# File 'lib/polars/expr.rb', line 365

def exclude(columns)
  if columns.is_a?(::String)
    columns = [columns]
    return _from_rbexpr(_rbexpr.exclude(columns))
  elsif !columns.is_a?(::Array)
    columns = [columns]
    return _from_rbexpr(_rbexpr.exclude_dtype(columns))
  end

  if !columns.all? { |a| a.is_a?(::String) } || !columns.all? { |a| Utils.is_polars_dtype(a) }
    raise ArgumentError, "input should be all string or all DataType"
  end

  if columns[0].is_a?(::String)
    _from_rbexpr(_rbexpr.exclude(columns))
  else
    _from_rbexpr(_rbexpr.exclude_dtype(columns))
  end
end

#exp ⇒ Expr

Compute the exponential, element-wise.

Examples:

df = Polars::DataFrame.new({"values" => [1.0, 2.0, 4.0]})
df.select(Polars.col("values").exp)
# =>
# shape: (3, 1)
# ┌──────────┐
# │ values   │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 2.718282 │
# │ 7.389056 │
# │ 54.59815 │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 289

def exp
  _from_rbexpr(_rbexpr.exp)
end

#explode ⇒ Expr

Explode a list or utf8 Series.

This means that every item is expanded to a new row.

Examples:

df = Polars::DataFrame.new({"b" => [[1, 2, 3], [4, 5, 6]]})
df.select(Polars.col("b").explode)
# =>
# shape: (6, 1)
# ┌─────┐
# │ b   │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 1   │
# │ 2   │
# │ 3   │
# │ 4   │
# │ 5   │
# │ 6   │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 3059

def explode
  _from_rbexpr(_rbexpr.explode)
end

#extend_constant(value, n) ⇒ Expr

Extend the Series with given number of values.

Examples:

df = Polars::DataFrame.new({"values" => [1, 2, 3]})
df.select(Polars.col("values").extend_constant(99, 2))
# =>
# shape: (5, 1)
# ┌────────┐
# │ values │
# │ ---    │
# │ i64    │
# ╞════════╡
# │ 1      │
# │ 2      │
# │ 3      │
# │ 99     │
# │ 99     │
# └────────┘

Parameters:

  • value (Object) —

    The value to extend the Series with. This value may be nil to fill with nulls.

  • n (Integer) —

    The number of values to extend.

Returns:



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# File 'lib/polars/expr.rb', line 6622

def extend_constant(value, n)
  _from_rbexpr(_rbexpr.extend_constant(value, n))
end

#fill_nan(fill_value) ⇒ Expr

Fill floating point NaN value with a fill value.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1.0, nil, Float::NAN],
    "b" => [4.0, Float::NAN, 6]
  }
)
df.fill_nan("zero")
# =>
# shape: (3, 2)
# ┌──────┬──────┐
# │ a    ┆ b    │
# │ ---  ┆ ---  │
# │ str  ┆ str  │
# ╞══════╪══════╡
# │ 1.0  ┆ 4.0  │
# │ null ┆ zero │
# │ zero ┆ 6.0  │
# └──────┴──────┘

Returns:



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# File 'lib/polars/expr.rb', line 1838

def fill_nan(fill_value)
  fill_value = Utils.parse_into_expression(fill_value, str_as_lit: true)
  _from_rbexpr(_rbexpr.fill_nan(fill_value))
end

#fill_null(value = nil, strategy: nil, limit: nil) ⇒ Expr

Fill null values using the specified value or strategy.

To interpolate over null values see interpolate.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, nil],
    "b" => [4, nil, 6]
  }
)
df.fill_null(strategy: "zero")
# =>
# shape: (3, 2)
# ┌─────┬─────┐
# │ a   ┆ b   │
# │ --- ┆ --- │
# │ i64 ┆ i64 │
# ╞═════╪═════╡
# │ 1   ┆ 4   │
# │ 2   ┆ 0   │
# │ 0   ┆ 6   │
# └─────┴─────┘
df.fill_null(99)
# =>
# shape: (3, 2)
# ┌─────┬─────┐
# │ a   ┆ b   │
# │ --- ┆ --- │
# │ i64 ┆ i64 │
# ╞═════╪═════╡
# │ 1   ┆ 4   │
# │ 2   ┆ 99  │
# │ 99  ┆ 6   │
# └─────┴─────┘
df.fill_null(strategy: "forward")
# =>
# shape: (3, 2)
# ┌─────┬─────┐
# │ a   ┆ b   │
# │ --- ┆ --- │
# │ i64 ┆ i64 │
# ╞═════╪═════╡
# │ 1   ┆ 4   │
# │ 2   ┆ 4   │
# │ 2   ┆ 6   │
# └─────┴─────┘

Parameters:

  • value (Object) (defaults to: nil) —

    Value used to fill null values.

  • strategy (nil, "forward", "backward", "min", "max", "mean", "zero", "one") (defaults to: nil) —

    Strategy used to fill null values.

  • limit (Integer) (defaults to: nil) —

    Number of consecutive null values to fill when using the 'forward' or 'backward' strategy.

Returns:



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# File 'lib/polars/expr.rb', line 1798

def fill_null(value = nil, strategy: nil, limit: nil)
  if !value.nil? && !strategy.nil?
    raise ArgumentError, "cannot specify both 'value' and 'strategy'."
  elsif value.nil? && strategy.nil?
    raise ArgumentError, "must specify either a fill 'value' or 'strategy'"
  elsif ["forward", "backward"].include?(strategy) && !limit.nil?
    raise ArgumentError, "can only specify 'limit' when strategy is set to 'backward' or 'forward'"
  end

  if !value.nil?
    value = Utils.parse_into_expression(value, str_as_lit: true)
    _from_rbexpr(_rbexpr.fill_null(value))
  else
    _from_rbexpr(_rbexpr.fill_null_with_strategy(strategy, limit))
  end
end

#filter(predicate) ⇒ Expr

Filter a single column.

Mostly useful in an aggregation context. If you want to filter on a DataFrame level, use LazyFrame#filter.

Examples:

df = Polars::DataFrame.new(
  {
    "group_col" => ["g1", "g1", "g2"],
    "b" => [1, 2, 3]
  }
)
(
  df.group_by("group_col").agg(
    [
      Polars.col("b").filter(Polars.col("b") < 2).sum.alias("lt"),
      Polars.col("b").filter(Polars.col("b") >= 2).sum.alias("gte")
    ]
  )
).sort("group_col")
# =>
# shape: (2, 3)
# ┌───────────┬─────┬─────┐
# │ group_col ┆ lt  ┆ gte │
# │ ---       ┆ --- ┆ --- │
# │ str       ┆ i64 ┆ i64 │
# ╞═══════════╪═════╪═════╡
# │ g1        ┆ 1   ┆ 2   │
# │ g2        ┆ 0   ┆ 3   │
# └───────────┴─────┴─────┘

Parameters:

  • predicate (Expr) —

    Boolean expression.

Returns:



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# File 'lib/polars/expr.rb', line 2819

def filter(predicate)
  _from_rbexpr(_rbexpr.filter(predicate._rbexpr))
end

#first ⇒ Expr

Get the first value.

Examples:

df = Polars::DataFrame.new({"a" => [1, 1, 2]})
df.select(Polars.col("a").first)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 1   │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2301

def first
  _from_rbexpr(_rbexpr.first)
end

#flatten ⇒ Expr

Explode a list or utf8 Series. This means that every item is expanded to a new row.

Alias for #explode.

Examples:

df = Polars::DataFrame.new(
  {
    "group" => ["a", "b", "b"],
    "values" => [[1, 2], [2, 3], [4]]
  }
)
df.group_by("group").agg(Polars.col("values").flatten)
# =>
# shape: (2, 2)
# ┌───────┬───────────┐
# │ group ┆ values    │
# │ ---   ┆ ---       │
# │ str   ┆ list[i64] │
# ╞═══════╪═══════════╡
# │ a     ┆ [1, 2]    │
# │ b     ┆ [2, 3, 4] │
# └───────┴───────────┘

Returns:



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# File 'lib/polars/expr.rb', line 3032

def flatten
  _from_rbexpr(_rbexpr.explode)
end

#floor ⇒ Expr

Rounds down to the nearest integer value.

Only works on floating point Series.

Examples:

df = Polars::DataFrame.new({"a" => [0.3, 0.5, 1.0, 1.1]})
df.select(Polars.col("a").floor)
# =>
# shape: (4, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 0.0 │
# │ 0.0 │
# │ 1.0 │
# │ 1.0 │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 1128

def floor
  _from_rbexpr(_rbexpr.floor)
end

#floordiv(other) ⇒ Expr

Method equivalent of integer division operator expr // other.

Examples:

df = Polars::DataFrame.new({"x" => [1, 2, 3, 4, 5]})
df.with_columns(
  Polars.col("x").truediv(2).alias("x/2"),
  Polars.col("x").floordiv(2).alias("x//2")
)
# =>
# shape: (5, 3)
# ┌─────┬─────┬──────┐
# │ x   ┆ x/2 ┆ x//2 │
# │ --- ┆ --- ┆ ---  │
# │ i64 ┆ f64 ┆ i64  │
# ╞═════╪═════╪══════╡
# │ 1   ┆ 0.5 ┆ 0    │
# │ 2   ┆ 1.0 ┆ 1    │
# │ 3   ┆ 1.5 ┆ 1    │
# │ 4   ┆ 2.0 ┆ 2    │
# │ 5   ┆ 2.5 ┆ 2    │
# └─────┴─────┴──────┘

Parameters:

  • other (Object) —

    Numeric literal or expression value.

Returns:



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# File 'lib/polars/expr.rb', line 3511

def floordiv(other)
  _from_rbexpr(_rbexpr.floordiv(_to_rbexpr(other)))
end

#forward_fill(limit: nil) ⇒ Expr

Fill missing values with the latest seen values.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, nil],
    "b" => [4, nil, 6]
  }
)
df.select(Polars.all.forward_fill)
# =>
# shape: (3, 2)
# ┌─────┬─────┐
# │ a   ┆ b   │
# │ --- ┆ --- │
# │ i64 ┆ i64 │
# ╞═════╪═════╡
# │ 1   ┆ 4   │
# │ 2   ┆ 4   │
# │ 2   ┆ 6   │
# └─────┴─────┘

Parameters:

  • limit (Integer) (defaults to: nil) —

    The number of consecutive null values to forward fill.

Returns:



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# File 'lib/polars/expr.rb', line 1869

def forward_fill(limit: nil)
  _from_rbexpr(_rbexpr.forward_fill(limit))
end

#gather(indices) ⇒ Expr Also known as: take

Take values by index.

Examples:

df = Polars::DataFrame.new(
  {
    "group" => [
      "one",
      "one",
      "one",
      "two",
      "two",
      "two"
    ],
    "value" => [1, 98, 2, 3, 99, 4]
  }
)
df.group_by("group", maintain_order: true).agg(Polars.col("value").take([2, 1]))
# =>
# shape: (2, 2)
# ┌───────┬───────────┐
# │ group ┆ value     │
# │ ---   ┆ ---       │
# │ str   ┆ list[i64] │
# ╞═══════╪═══════════╡
# │ one   ┆ [2, 98]   │
# │ two   ┆ [4, 99]   │
# └───────┴───────────┘

Parameters:

  • indices (Expr) —

    An expression that leads to a :u32 dtyped Series.

Returns:



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# File 'lib/polars/expr.rb', line 1630

def gather(indices)
  if indices.is_a?(::Array)
    indices_lit = Polars.lit(Series.new("", indices, dtype: :u32))._rbexpr
  else
    indices_lit = Utils.parse_into_expression(indices, str_as_lit: false)
  end
  _from_rbexpr(_rbexpr.gather(indices_lit))
end

#gather_every(n, offset = 0) ⇒ Expr Also known as: take_every

Take every nth value in the Series and return as a new Series.

Examples:

df = Polars::DataFrame.new({"foo" => [1, 2, 3, 4, 5, 6, 7, 8, 9]})
df.select(Polars.col("foo").gather_every(3))
# =>
# shape: (3, 1)
# ┌─────┐
# │ foo │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 1   │
# │ 4   │
# │ 7   │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 3081

def gather_every(n, offset = 0)
  _from_rbexpr(_rbexpr.gather_every(n, offset))
end

#ge(other) ⇒ Expr

Method equivalent of "greater than or equal" operator expr >= other.

Examples:

df = Polars::DataFrame.new(
  {
    "x" => [5.0, 4.0, Float::NAN, 2.0],
    "y" => [5.0, 3.0, Float::NAN, 1.0]
  }
)
df.with_columns(
  Polars.col("x").ge(Polars.col("y")).alias("x >= y")
)
# =>
# shape: (4, 3)
# ┌─────┬─────┬────────┐
# │ x   ┆ y   ┆ x >= y │
# │ --- ┆ --- ┆ ---    │
# │ f64 ┆ f64 ┆ bool   │
# ╞═════╪═════╪════════╡
# │ 5.0 ┆ 5.0 ┆ true   │
# │ 4.0 ┆ 3.0 ┆ true   │
# │ NaN ┆ NaN ┆ true   │
# │ 2.0 ┆ 1.0 ┆ true   │
# └─────┴─────┴────────┘

Parameters:

  • other (Object) —

    A literal or expression value to compare with.

Returns:



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# File 'lib/polars/expr.rb', line 3263

def ge(other)
  self >= other
end

#get(index) ⇒ Expr

Return a single value by index.

Examples:

df = Polars::DataFrame.new(
  {
    "group" => [
      "one",
      "one",
      "one",
      "two",
      "two",
      "two"
    ],
    "value" => [1, 98, 2, 3, 99, 4]
  }
)
df.group_by("group", maintain_order: true).agg(Polars.col("value").get(1))
# =>
# shape: (2, 2)
# ┌───────┬───────┐
# │ group ┆ value │
# │ ---   ┆ ---   │
# │ str   ┆ i64   │
# ╞═══════╪═══════╡
# │ one   ┆ 98    │
# │ two   ┆ 99    │
# └───────┴───────┘

Parameters:

  • index (Object) —

    An expression that leads to a UInt32 index.

Returns:



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# File 'lib/polars/expr.rb', line 1672

def get(index)
  index_lit = Utils.parse_into_expression(index)
  _from_rbexpr(_rbexpr.get(index_lit))
end

#gt(other) ⇒ Expr

Method equivalent of "greater than" operator expr > other.

Examples:

df = Polars::DataFrame.new(
  {
    "x" => [5.0, 4.0, Float::NAN, 2.0],
    "y" => [5.0, 3.0, Float::NAN, 1.0]
  }
)
df.with_columns(
    Polars.col("x").gt(Polars.col("y")).alias("x > y")
)
# =>
# shape: (4, 3)
# ┌─────┬─────┬───────┐
# │ x   ┆ y   ┆ x > y │
# │ --- ┆ --- ┆ ---   │
# │ f64 ┆ f64 ┆ bool  │
# ╞═════╪═════╪═══════╡
# │ 5.0 ┆ 5.0 ┆ false │
# │ 4.0 ┆ 3.0 ┆ true  │
# │ NaN ┆ NaN ┆ false │
# │ 2.0 ┆ 1.0 ┆ true  │
# └─────┴─────┴───────┘

Parameters:

  • other (Object) —

    A literal or expression value to compare with.

Returns:



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# File 'lib/polars/expr.rb', line 3296

def gt(other)
  self > other
end

#head(n = 10) ⇒ Expr

Get the first n rows.

Examples:

df = Polars::DataFrame.new({"foo" => [1, 2, 3, 4, 5, 6, 7]})
df.head(3)
# =>
# shape: (3, 1)
# ┌─────┐
# │ foo │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 1   │
# │ 2   │
# │ 3   │
# └─────┘

Parameters:

  • n (Integer) (defaults to: 10) —

    Number of rows to return.

Returns:



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# File 'lib/polars/expr.rb', line 3107

def head(n = 10)
  _from_rbexpr(_rbexpr.head(n))
end

#implode ⇒ Expr

Aggregate to list.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, 3],
    "b" => [4, 5, 6]
  }
)
df.select(Polars.all.implode)
# =>
# shape: (1, 2)
# ┌───────────┬───────────┐
# │ a         ┆ b         │
# │ ---       ┆ ---       │
# │ list[i64] ┆ list[i64] │
# ╞═══════════╪═══════════╡
# │ [1, 2, 3] ┆ [4, 5, 6] │
# └───────────┴───────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6878

def implode
  _from_rbexpr(_rbexpr.implode)
end

#interpolate(method: "linear") ⇒ Expr

Fill nulls with linear interpolation over missing values.

Can also be used to regrid data to a new grid - see examples below.

Examples:

Fill nulls with linear interpolation

df = Polars::DataFrame.new(
  {
    "a" => [1, nil, 3],
    "b" => [1.0, Float::NAN, 3.0]
  }
)
df.select(Polars.all.interpolate)
# =>
# shape: (3, 2)
# ┌─────┬─────┐
# │ a   ┆ b   │
# │ --- ┆ --- │
# │ f64 ┆ f64 │
# ╞═════╪═════╡
# │ 1.0 ┆ 1.0 │
# │ 2.0 ┆ NaN │
# │ 3.0 ┆ 3.0 │
# └─────┴─────┘

Returns:



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# File 'lib/polars/expr.rb', line 3993

def interpolate(method: "linear")
  _from_rbexpr(_rbexpr.interpolate(method))
end

#is_between(lower_bound, upper_bound, closed: "both") ⇒ Expr

Check if this expression is between start and end.

Examples:

df = Polars::DataFrame.new({"num" => [1, 2, 3, 4, 5]})
df.with_columns(Polars.col("num").is_between(2, 4).alias("is_between"))
# =>
# shape: (5, 2)
# ┌─────┬────────────┐
# │ num ┆ is_between │
# │ --- ┆ ---        │
# │ i64 ┆ bool       │
# ╞═════╪════════════╡
# │ 1   ┆ false      │
# │ 2   ┆ true       │
# │ 3   ┆ true       │
# │ 4   ┆ true       │
# │ 5   ┆ false      │
# └─────┴────────────┘

Use the closed argument to include or exclude the values at the bounds:

df.with_columns(
  Polars.col("num").is_between(2, 4, closed: "left").alias("is_between")
)
# =>
# shape: (5, 2)
# ┌─────┬────────────┐
# │ num ┆ is_between │
# │ --- ┆ ---        │
# │ i64 ┆ bool       │
# ╞═════╪════════════╡
# │ 1   ┆ false      │
# │ 2   ┆ true       │
# │ 3   ┆ true       │
# │ 4   ┆ false      │
# │ 5   ┆ false      │
# └─────┴────────────┘

You can also use strings as well as numeric/temporal values:

df = Polars::DataFrame.new({"a" => ["a", "b", "c", "d", "e"]})
df.with_columns(
  Polars.col("a")
    .is_between(Polars.lit("a"), Polars.lit("c"), closed: "both")
    .alias("is_between")
)
# =>
# shape: (5, 2)
# ┌─────┬────────────┐
# │ a   ┆ is_between │
# │ --- ┆ ---        │
# │ str ┆ bool       │
# ╞═════╪════════════╡
# │ a   ┆ true       │
# │ b   ┆ true       │
# │ c   ┆ true       │
# │ d   ┆ false      │
# │ e   ┆ false      │
# └─────┴────────────┘

Parameters:

  • lower_bound (Object) —

    Lower bound as primitive type or datetime.

  • upper_bound (Object) —

    Upper bound as primitive type or datetime.

  • closed ("both", "left", "right", "none") (defaults to: "both") —

    Define which sides of the interval are closed (inclusive).

Returns:



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# File 'lib/polars/expr.rb', line 3849

def is_between(lower_bound, upper_bound, closed: "both")
  lower_bound = Utils.parse_into_expression(lower_bound)
  upper_bound = Utils.parse_into_expression(upper_bound)

  _from_rbexpr(
    _rbexpr.is_between(lower_bound, upper_bound, closed)
  )
end

#is_duplicated ⇒ Expr

Get mask of duplicated values.

Examples:

df = Polars::DataFrame.new({"a" => [1, 1, 2]})
df.select(Polars.col("a").is_duplicated)
# =>
# shape: (3, 1)
# ┌───────┐
# │ a     │
# │ ---   │
# │ bool  │
# ╞═══════╡
# │ true  │
# │ true  │
# │ false │
# └───────┘

Returns:



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# File 'lib/polars/expr.rb', line 2458

def is_duplicated
  _from_rbexpr(_rbexpr.is_duplicated)
end

#is_finite ⇒ Expr

Returns a boolean Series indicating which values are finite.

Examples:

df = Polars::DataFrame.new(
  {
    "A" => [1.0, 2],
    "B" => [3.0, Float::INFINITY]
  }
)
df.select(Polars.all.is_finite)
# =>
# shape: (2, 2)
# ┌──────┬───────┐
# │ A    ┆ B     │
# │ ---  ┆ ---   │
# │ bool ┆ bool  │
# ╞══════╪═══════╡
# │ true ┆ true  │
# │ true ┆ false │
# └──────┴───────┘

Returns:



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# File 'lib/polars/expr.rb', line 614

def is_finite
  _from_rbexpr(_rbexpr.is_finite)
end

#is_first_distinct ⇒ Expr Also known as: is_first

Get a mask of the first unique value.

Examples:

df = Polars::DataFrame.new(
  {
    "num" => [1, 2, 3, 1, 5]
  }
)
df.with_column(Polars.col("num").is_first.alias("is_first"))
# =>
# shape: (5, 2)
# ┌─────┬──────────┐
# │ num ┆ is_first │
# │ --- ┆ ---      │
# │ i64 ┆ bool     │
# ╞═════╪══════════╡
# │ 1   ┆ true     │
# │ 2   ┆ true     │
# │ 3   ┆ true     │
# │ 1   ┆ false    │
# │ 5   ┆ true     │
# └─────┴──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 2435

def is_first_distinct
  _from_rbexpr(_rbexpr.is_first_distinct)
end

#is_in(other) ⇒ Expr Also known as: in?

Check if elements of this expression are present in the other Series.

Examples:

df = Polars::DataFrame.new(
  {"sets" => [[1, 2, 3], [1, 2], [9, 10]], "optional_members" => [1, 2, 3]}
)
df.select([Polars.col("optional_members").is_in("sets").alias("contains")])
# =>
# shape: (3, 1)
# ┌──────────┐
# │ contains │
# │ ---      │
# │ bool     │
# ╞══════════╡
# │ true     │
# │ true     │
# │ false    │
# └──────────┘

Parameters:

  • other (Object) —

    Series or sequence of primitive type.

Returns:



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# File 'lib/polars/expr.rb', line 3734

def is_in(other)
  if other.is_a?(::Array)
    if other.length == 0
      other = Polars.lit(nil)._rbexpr
    else
      other = Polars.lit(Series.new(other))._rbexpr
    end
  else
    other = Utils.parse_into_expression(other, str_as_lit: false)
  end
  _from_rbexpr(_rbexpr.is_in(other))
end

#is_infinite ⇒ Expr

Returns a boolean Series indicating which values are infinite.

Examples:

df = Polars::DataFrame.new(
  {
    "A" => [1.0, 2],
    "B" => [3.0, Float::INFINITY]
  }
)
df.select(Polars.all.is_infinite)
# =>
# shape: (2, 2)
# ┌───────┬───────┐
# │ A     ┆ B     │
# │ ---   ┆ ---   │
# │ bool  ┆ bool  │
# ╞═══════╪═══════╡
# │ false ┆ false │
# │ false ┆ true  │
# └───────┴───────┘

Returns:



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# File 'lib/polars/expr.rb', line 640

def is_infinite
  _from_rbexpr(_rbexpr.is_infinite)
end

#is_nan ⇒ Expr

Note:

Floating point NaN (Not A Number) should not be confused with missing data represented as nil.

Returns a boolean Series indicating which values are NaN.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, nil, 1, 5],
    "b" => [1.0, 2.0, Float::NAN, 1.0, 5.0]
  }
)
df.with_column(Polars.col(Polars::Float64).is_nan.suffix("_isnan"))
# =>
# shape: (5, 3)
# ┌──────┬─────┬─────────┐
# │ a    ┆ b   ┆ b_isnan │
# │ ---  ┆ --- ┆ ---     │
# │ i64  ┆ f64 ┆ bool    │
# ╞══════╪═════╪═════════╡
# │ 1    ┆ 1.0 ┆ false   │
# │ 2    ┆ 2.0 ┆ false   │
# │ null ┆ NaN ┆ true    │
# │ 1    ┆ 1.0 ┆ false   │
# │ 5    ┆ 5.0 ┆ false   │
# └──────┴─────┴─────────┘

Returns:



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# File 'lib/polars/expr.rb', line 673

def is_nan
  _from_rbexpr(_rbexpr.is_nan)
end

#is_not ⇒ Expr Also known as: not_

Negate a boolean expression.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [true, false, false],
    "b" => ["a", "b", nil]
  }
)
# =>
# shape: (3, 2)
# ┌───────┬──────┐
# │ a     ┆ b    │
# │ ---   ┆ ---  │
# │ bool  ┆ str  │
# ╞═══════╪══════╡
# │ true  ┆ a    │
# │ false ┆ b    │
# │ false ┆ null │
# └───────┴──────┘
df.select(Polars.col("a").is_not)
# =>
# shape: (3, 1)
# ┌───────┐
# │ a     │
# │ ---   │
# │ bool  │
# ╞═══════╡
# │ false │
# │ true  │
# │ true  │
# └───────┘

Returns:



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# File 'lib/polars/expr.rb', line 529

def is_not
  _from_rbexpr(_rbexpr.not_)
end

#is_not_nan ⇒ Expr

Note:

Floating point NaN (Not A Number) should not be confused with missing data represented as nil.

Returns a boolean Series indicating which values are not NaN.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, nil, 1, 5],
    "b" => [1.0, 2.0, Float::NAN, 1.0, 5.0]
  }
)
df.with_column(Polars.col(Polars::Float64).is_not_nan.suffix("_is_not_nan"))
# =>
# shape: (5, 3)
# ┌──────┬─────┬──────────────┐
# │ a    ┆ b   ┆ b_is_not_nan │
# │ ---  ┆ --- ┆ ---          │
# │ i64  ┆ f64 ┆ bool         │
# ╞══════╪═════╪══════════════╡
# │ 1    ┆ 1.0 ┆ true         │
# │ 2    ┆ 2.0 ┆ true         │
# │ null ┆ NaN ┆ false        │
# │ 1    ┆ 1.0 ┆ true         │
# │ 5    ┆ 5.0 ┆ true         │
# └──────┴─────┴──────────────┘

Returns:



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# File 'lib/polars/expr.rb', line 706

def is_not_nan
  _from_rbexpr(_rbexpr.is_not_nan)
end

#is_not_null ⇒ Expr

Returns a boolean Series indicating which values are not null.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, nil, 1, 5],
    "b" => [1.0, 2.0, Float::NAN, 1.0, 5.0]
  }
)
df.with_column(Polars.all.is_not_null.suffix("_not_null"))
# =>
# shape: (5, 4)
# ┌──────┬─────┬────────────┬────────────┐
# │ a    ┆ b   ┆ a_not_null ┆ b_not_null │
# │ ---  ┆ --- ┆ ---        ┆ ---        │
# │ i64  ┆ f64 ┆ bool       ┆ bool       │
# ╞══════╪═════╪════════════╪════════════╡
# │ 1    ┆ 1.0 ┆ true       ┆ true       │
# │ 2    ┆ 2.0 ┆ true       ┆ true       │
# │ null ┆ NaN ┆ false      ┆ true       │
# │ 1    ┆ 1.0 ┆ true       ┆ true       │
# │ 5    ┆ 5.0 ┆ true       ┆ true       │
# └──────┴─────┴────────────┴────────────┘

Returns:



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# File 'lib/polars/expr.rb', line 588

def is_not_null
  _from_rbexpr(_rbexpr.is_not_null)
end

#is_null ⇒ Expr

Returns a boolean Series indicating which values are null.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, nil, 1, 5],
    "b" => [1.0, 2.0, Float::NAN, 1.0, 5.0]
  }
)
df.with_column(Polars.all.is_null.suffix("_isnull"))
# =>
# shape: (5, 4)
# ┌──────┬─────┬──────────┬──────────┐
# │ a    ┆ b   ┆ a_isnull ┆ b_isnull │
# │ ---  ┆ --- ┆ ---      ┆ ---      │
# │ i64  ┆ f64 ┆ bool     ┆ bool     │
# ╞══════╪═════╪══════════╪══════════╡
# │ 1    ┆ 1.0 ┆ false    ┆ false    │
# │ 2    ┆ 2.0 ┆ false    ┆ false    │
# │ null ┆ NaN ┆ true     ┆ false    │
# │ 1    ┆ 1.0 ┆ false    ┆ false    │
# │ 5    ┆ 5.0 ┆ false    ┆ false    │
# └──────┴─────┴──────────┴──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 559

def is_null
  _from_rbexpr(_rbexpr.is_null)
end

#is_unique ⇒ Expr

Get mask of unique values.

Examples:

df = Polars::DataFrame.new({"a" => [1, 1, 2]})
df.select(Polars.col("a").is_unique)
# =>
# shape: (3, 1)
# ┌───────┐
# │ a     │
# │ ---   │
# │ bool  │
# ╞═══════╡
# │ false │
# │ false │
# │ true  │
# └───────┘

Returns:



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# File 'lib/polars/expr.rb', line 2407

def is_unique
  _from_rbexpr(_rbexpr.is_unique)
end

#keep_name ⇒ Expr

Keep the original root name of the expression.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2],
    "b" => [3, 4]
  }
)
df.with_columns([(Polars.col("a") * 9).alias("c").keep_name])
# =>
# shape: (2, 2)
# ┌─────┬─────┐
# │ a   ┆ b   │
# │ --- ┆ --- │
# │ i64 ┆ i64 │
# ╞═════╪═════╡
# │ 9   ┆ 3   │
# │ 18  ┆ 4   │
# └─────┴─────┘

Returns:



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# File 'lib/polars/expr.rb', line 407

def keep_name
  name.keep
end

#kurtosis(fisher: true, bias: true) ⇒ Expr

Compute the kurtosis (Fisher or Pearson) of a dataset.

Kurtosis is the fourth central moment divided by the square of the variance. If Fisher's definition is used, then 3.0 is subtracted from the result to give 0.0 for a normal distribution. If bias is False then the kurtosis is calculated using k statistics to eliminate bias coming from biased moment estimators

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3, 2, 1]})
df.select(Polars.col("a").kurtosis)
# =>
# shape: (1, 1)
# ┌───────────┐
# │ a         │
# │ ---       │
# │ f64       │
# ╞═══════════╡
# │ -1.153061 │
# └───────────┘

Parameters:

  • fisher (Boolean) (defaults to: true) —

    If true, Fisher's definition is used (normal ==> 0.0). If false, Pearson's definition is used (normal ==> 3.0).

  • bias (Boolean) (defaults to: true) —

    If false, the calculations are corrected for statistical bias.

Returns:



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# File 'lib/polars/expr.rb', line 5958

def kurtosis(fisher: true, bias: true)
  _from_rbexpr(_rbexpr.kurtosis(fisher, bias))
end

#last ⇒ Expr

Get the last value.

Examples:

df = Polars::DataFrame.new({"a" => [1, 1, 2]})
df.select(Polars.col("a").last)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 2   │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2321

def last
  _from_rbexpr(_rbexpr.last)
end

#le(other) ⇒ Expr

Method equivalent of "less than or equal" operator expr <= other.

Examples:

df = Polars::DataFrame.new(
  {
    "x" => [5.0, 4.0, Float::NAN, 0.5],
    "y" => [5.0, 3.5, Float::NAN, 2.0]
  }
)
df.with_columns(
  Polars.col("x").le(Polars.col("y")).alias("x <= y")
)
# =>
# shape: (4, 3)
# ┌─────┬─────┬────────┐
# │ x   ┆ y   ┆ x <= y │
# │ --- ┆ --- ┆ ---    │
# │ f64 ┆ f64 ┆ bool   │
# ╞═════╪═════╪════════╡
# │ 5.0 ┆ 5.0 ┆ true   │
# │ 4.0 ┆ 3.5 ┆ false  │
# │ NaN ┆ NaN ┆ true   │
# │ 0.5 ┆ 2.0 ┆ true   │
# └─────┴─────┴────────┘

Parameters:

  • other (Object) —

    A literal or expression value to compare with.

Returns:



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# File 'lib/polars/expr.rb', line 3329

def le(other)
  self <= other
end

#len ⇒ Expr Also known as: length

Count the number of values in this expression.

Examples:

df = Polars::DataFrame.new({"a" => [8, 9, 10], "b" => [nil, 4, 4]})
df.select(Polars.all.len)
# =>
# shape: (1, 2)
# ┌─────┬─────┐
# │ a   ┆ b   │
# │ --- ┆ --- │
# │ u32 ┆ u32 │
# ╞═════╪═════╡
# │ 3   ┆ 3   │
# └─────┴─────┘

Returns:



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# File 'lib/polars/expr.rb', line 781

def len
  _from_rbexpr(_rbexpr.len)
end

#limit(n = 10) ⇒ Expr

Get the first n rows.

Alias for #head.

Examples:

df = Polars::DataFrame.new({"foo" => [1, 2, 3, 4, 5, 6, 7]})
df.select(Polars.col("foo").limit(3))
# =>
# shape: (3, 1)
# ┌─────┐
# │ foo │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 1   │
# │ 2   │
# │ 3   │
# └─────┘

Parameters:

  • n (Integer) (defaults to: 10) —

    Number of rows to return.

Returns:



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# File 'lib/polars/expr.rb', line 3159

def limit(n = 10)
  head(n)
end

#list ⇒ ListExpr

Create an object namespace of all list related methods.

Returns:



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# File 'lib/polars/expr.rb', line 7233

def list
  ListExpr.new(self)
end

#log(base = Math::E) ⇒ Expr

Compute the logarithm to a given base.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3]})
df.select(Polars.col("a").log(2))
# =>
# shape: (3, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 0.0      │
# │ 1.0      │
# │ 1.584963 │
# └──────────┘

Parameters:

  • base (Float) (defaults to: Math::E) —

    Given base, defaults to e.

Returns:



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# File 'lib/polars/expr.rb', line 6736

def log(base = Math::E)
  _from_rbexpr(_rbexpr.log(base))
end

#log10 ⇒ Expr

Compute the base 10 logarithm of the input array, element-wise.

Examples:

df = Polars::DataFrame.new({"values" => [1.0, 2.0, 4.0]})
df.select(Polars.col("values").log10)
# =>
# shape: (3, 1)
# ┌─────────┐
# │ values  │
# │ ---     │
# │ f64     │
# ╞═════════╡
# │ 0.0     │
# │ 0.30103 │
# │ 0.60206 │
# └─────────┘

Returns:



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# File 'lib/polars/expr.rb', line 267

def log10
  log(10)
end

#lower_bound ⇒ Expr

Calculate the lower bound.

Returns a unit Series with the lowest value possible for the dtype of this expression.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3, 2, 1]})
df.select(Polars.col("a").lower_bound)
# =>
# shape: (1, 1)
# ┌──────────────────────┐
# │ a                    │
# │ ---                  │
# │ i64                  │
# ╞══════════════════════╡
# │ -9223372036854775808 │
# └──────────────────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6080

def lower_bound
  _from_rbexpr(_rbexpr.lower_bound)
end

#lt(other) ⇒ Expr

Method equivalent of "less than" operator expr < other.

Examples:

df = Polars::DataFrame.new(
  {
    "x" => [1.0, 2.0, Float::NAN, 3.0],
    "y" => [2.0, 2.0, Float::NAN, 4.0]
  }
)
df.with_columns(
  Polars.col("x").lt(Polars.col("y")).alias("x < y"),
)
# =>
# shape: (4, 3)
# ┌─────┬─────┬───────┐
# │ x   ┆ y   ┆ x < y │
# │ --- ┆ --- ┆ ---   │
# │ f64 ┆ f64 ┆ bool  │
# ╞═════╪═════╪═══════╡
# │ 1.0 ┆ 2.0 ┆ true  │
# │ 2.0 ┆ 2.0 ┆ false │
# │ NaN ┆ NaN ┆ false │
# │ 3.0 ┆ 4.0 ┆ true  │
# └─────┴─────┴───────┘

Parameters:

  • other (Object) —

    A literal or expression value to compare with.

Returns:



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# File 'lib/polars/expr.rb', line 3362

def lt(other)
  self < other
end

#map_alias(&f) ⇒ Expr

Rename the output of an expression by mapping a function over the root name.

Examples:

df = Polars::DataFrame.new(
  {
    "A" => [1, 2],
    "B" => [3, 4]
  }
)
df.select(
  Polars.all.reverse.map_alias { |colName| colName + "_reverse" }
)
# =>
# shape: (2, 2)
# ┌───────────┬───────────┐
# │ A_reverse ┆ B_reverse │
# │ ---       ┆ ---       │
# │ i64       ┆ i64       │
# ╞═══════════╪═══════════╡
# │ 2         ┆ 4         │
# │ 1         ┆ 3         │
# └───────────┴───────────┘

Returns:



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# File 'lib/polars/expr.rb', line 489

def map_alias(&f)
  name.map(&f)
end

#max ⇒ Expr

Get maximum value.

Examples:

df = Polars::DataFrame.new({"a" => [-1.0, Float::NAN, 1.0]})
df.select(Polars.col("a").max)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 1.0 │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2001

def max
  _from_rbexpr(_rbexpr.max)
end

#mean ⇒ Expr

Get mean value.

Examples:

df = Polars::DataFrame.new({"a" => [-1, 0, 1]})
df.select(Polars.col("a").mean)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 0.0 │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2105

def mean
  _from_rbexpr(_rbexpr.mean)
end

#median ⇒ Expr

Get median value using linear interpolation.

Examples:

df = Polars::DataFrame.new({"a" => [-1, 0, 1]})
df.select(Polars.col("a").median)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 0.0 │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2125

def median
  _from_rbexpr(_rbexpr.median)
end

#meta ⇒ MetaExpr

Create an object namespace of all meta related expression methods.

Returns:



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# File 'lib/polars/expr.rb', line 7268

def meta
  MetaExpr.new(self)
end

#min ⇒ Expr

Get minimum value.

Examples:

df = Polars::DataFrame.new({"a" => [-1.0, Float::NAN, 1.0]})
df.select(Polars.col("a").min)
# =>
# shape: (1, 1)
# ┌──────┐
# │ a    │
# │ ---  │
# │ f64  │
# ╞══════╡
# │ -1.0 │
# └──────┘

Returns:



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# File 'lib/polars/expr.rb', line 2021

def min
  _from_rbexpr(_rbexpr.min)
end

#mod(other) ⇒ Expr

Method equivalent of modulus operator expr % other.

Examples:

df = Polars::DataFrame.new({"x" => [0, 1, 2, 3, 4]})
df.with_columns(Polars.col("x").mod(2).alias("x%2"))
# =>
# shape: (5, 2)
# ┌─────┬─────┐
# │ x   ┆ x%2 │
# │ --- ┆ --- │
# │ i64 ┆ i64 │
# ╞═════╪═════╡
# │ 0   ┆ 0   │
# │ 1   ┆ 1   │
# │ 2   ┆ 0   │
# │ 3   ┆ 1   │
# │ 4   ┆ 0   │
# └─────┴─────┘

Parameters:

  • other (Object) —

    Numeric literal or expression value.

Returns:



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# File 'lib/polars/expr.rb', line 3538

def mod(other)
  self % other
end

#mode ⇒ Expr

Compute the most occurring value(s).

Can return multiple Values.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 1, 2, 3],
    "b" => [1, 1, 2, 2]
  }
)
df.select(Polars.all.mode.first)
# =>
# shape: (2, 2)
# ┌─────┬─────┐
# │ a   ┆ b   │
# │ --- ┆ --- │
# │ i64 ┆ i64 │
# ╞═════╪═════╡
# │ 1   ┆ 1   │
# │ 1   ┆ 2   │
# └─────┴─────┘

Returns:



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# File 'lib/polars/expr.rb', line 1236

def mode
  _from_rbexpr(_rbexpr.mode)
end

#mul(other) ⇒ Expr

Method equivalent of multiplication operator expr * other.

Examples:

df = Polars::DataFrame.new({"x" => [1, 2, 4, 8, 16]})
df.with_columns(
  Polars.col("x").mul(2).alias("x*2"),
  Polars.col("x").mul(Polars.col("x").log(2)).alias("x * xlog2"),
)
# =>
# shape: (5, 3)
# ┌─────┬─────┬───────────┐
# │ x   ┆ x*2 ┆ x * xlog2 │
# │ --- ┆ --- ┆ ---       │
# │ i64 ┆ i64 ┆ f64       │
# ╞═════╪═════╪═══════════╡
# │ 1   ┆ 2   ┆ 0.0       │
# │ 2   ┆ 4   ┆ 2.0       │
# │ 4   ┆ 8   ┆ 8.0       │
# │ 8   ┆ 16  ┆ 24.0      │
# │ 16  ┆ 32  ┆ 64.0      │
# └─────┴─────┴───────────┘

Parameters:

  • other (Object) —

    Numeric literal or expression value.

Returns:



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# File 'lib/polars/expr.rb', line 3568

def mul(other)
  self * other
end

#n_unique ⇒ Expr

Count unique values.

Examples:

df = Polars::DataFrame.new({"a" => [1, 1, 2]})
df.select(Polars.col("a").n_unique)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ u32 │
# ╞═════╡
# │ 2   │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2165

def n_unique
  _from_rbexpr(_rbexpr.n_unique)
end

#name ⇒ NameExpr

Create an object namespace of all expressions that modify expression names.

Returns:



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# File 'lib/polars/expr.rb', line 7275

def name
  NameExpr.new(self)
end

#nan_max ⇒ Expr

Get maximum value, but propagate/poison encountered NaN values.

Examples:

df = Polars::DataFrame.new({"a" => [0.0, Float::NAN]})
df.select(Polars.col("a").nan_max)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ NaN │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2041

def nan_max
  _from_rbexpr(_rbexpr.nan_max)
end

#nan_min ⇒ Expr

Get minimum value, but propagate/poison encountered NaN values.

Examples:

df = Polars::DataFrame.new({"a" => [0.0, Float::NAN]})
df.select(Polars.col("a").nan_min)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ NaN │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2061

def nan_min
  _from_rbexpr(_rbexpr.nan_min)
end

#ne(other) ⇒ Expr

Method equivalent of inequality operator expr != other.

Examples:

df = Polars::DataFrame.new(
  {
    "x" => [1.0, 2.0, Float::NAN, 4.0],
    "y" => [2.0, 2.0, Float::NAN, 4.0]
  }
)
df.with_columns(
  Polars.col("x").ne(Polars.col("y")).alias("x != y"),
)
# =>
# shape: (4, 3)
# ┌─────┬─────┬────────┐
# │ x   ┆ y   ┆ x != y │
# │ --- ┆ --- ┆ ---    │
# │ f64 ┆ f64 ┆ bool   │
# ╞═════╪═════╪════════╡
# │ 1.0 ┆ 2.0 ┆ true   │
# │ 2.0 ┆ 2.0 ┆ false  │
# │ NaN ┆ NaN ┆ false  │
# │ 4.0 ┆ 4.0 ┆ false  │
# └─────┴─────┴────────┘

Parameters:

  • other (Object) —

    A literal or expression value to compare with.

Returns:



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# File 'lib/polars/expr.rb', line 3395

def ne(other)
  self != other
end

#ne_missing(other) ⇒ Expr

Method equivalent of equality operator expr != other where None == None.

This differs from default ne where null values are propagated.

Examples:

df = Polars::DataFrame.new(
  {
    "x" => [1.0, 2.0, Float::NAN, 4.0, nil, nil],
    "y" => [2.0, 2.0, Float::NAN, 4.0, 5.0, nil]
  }
)
df.with_columns(
  Polars.col("x").ne(Polars.col("y")).alias("x ne y"),
  Polars.col("x").ne_missing(Polars.col("y")).alias("x ne_missing y")
)
# =>
# shape: (6, 4)
# ┌──────┬──────┬────────┬────────────────┐
# │ x    ┆ y    ┆ x ne y ┆ x ne_missing y │
# │ ---  ┆ ---  ┆ ---    ┆ ---            │
# │ f64  ┆ f64  ┆ bool   ┆ bool           │
# ╞══════╪══════╪════════╪════════════════╡
# │ 1.0  ┆ 2.0  ┆ true   ┆ true           │
# │ 2.0  ┆ 2.0  ┆ false  ┆ false          │
# │ NaN  ┆ NaN  ┆ false  ┆ false          │
# │ 4.0  ┆ 4.0  ┆ false  ┆ false          │
# │ null ┆ 5.0  ┆ null   ┆ true           │
# │ null ┆ null ┆ null   ┆ false          │
# └──────┴──────┴────────┴────────────────┘

Parameters:

  • other (Object) —

    A literal or expression value to compare with.

Returns:



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# File 'lib/polars/expr.rb', line 3433

def ne_missing(other)
  other = Utils.parse_into_expression(other, str_as_lit: true)
  _from_rbexpr(_rbexpr.neq_missing(other))
end

#neg ⇒ Expr

Method equivalent of unary minus operator -expr.

Examples:

df = Polars::DataFrame.new({"a" => [-1, 0, 2, nil]})
df.with_columns(Polars.col("a").neg)
# =>
# shape: (4, 1)
# ┌──────┐
# │ a    │
# │ ---  │
# │ i64  │
# ╞══════╡
# │ 1    │
# │ 0    │
# │ -2   │
# │ null │
# └──────┘

Returns:



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# File 'lib/polars/expr.rb', line 3621

def neg
  -self
end

#null_count ⇒ Expr

Count null values.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [nil, 1, nil],
    "b" => [1, 2, 3]
  }
)
df.select(Polars.all.null_count)
# =>
# shape: (1, 2)
# ┌─────┬─────┐
# │ a   ┆ b   │
# │ --- ┆ --- │
# │ u32 ┆ u32 │
# ╞═════╪═════╡
# │ 2   ┆ 0   │
# └─────┴─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2213

def null_count
  _from_rbexpr(_rbexpr.null_count)
end

#over(expr) ⇒ Expr

Apply window function over a subgroup.

This is similar to a group by + aggregation + self join. Or similar to window functions in Postgres.

Examples:

df = Polars::DataFrame.new(
  {
    "groups" => ["g1", "g1", "g2"],
    "values" => [1, 2, 3]
  }
)
df.with_column(
  Polars.col("values").max.over("groups").alias("max_by_group")
)
# =>
# shape: (3, 3)
# ┌────────┬────────┬──────────────┐
# │ groups ┆ values ┆ max_by_group │
# │ ---    ┆ ---    ┆ ---          │
# │ str    ┆ i64    ┆ i64          │
# ╞════════╪════════╪══════════════╡
# │ g1     ┆ 1      ┆ 2            │
# │ g1     ┆ 2      ┆ 2            │
# │ g2     ┆ 3      ┆ 3            │
# └────────┴────────┴──────────────┘
df = Polars::DataFrame.new(
  {
    "groups" => [1, 1, 2, 2, 1, 2, 3, 3, 1],
    "values" => [1, 2, 3, 4, 5, 6, 7, 8, 8]
  }
)
df.lazy
  .select([Polars.col("groups").sum.over("groups")])
  .collect
# =>
# shape: (9, 1)
# ┌────────┐
# │ groups │
# │ ---    │
# │ i64    │
# ╞════════╡
# │ 4      │
# │ 4      │
# │ 6      │
# │ 6      │
# │ 4      │
# │ 6      │
# │ 6      │
# │ 6      │
# │ 4      │
# └────────┘

Parameters:

  • expr (Object) —

    Column(s) to group by.

Returns:



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# File 'lib/polars/expr.rb', line 2384

def over(expr)
  rbexprs = Utils.parse_into_list_of_expressions(expr)
  _from_rbexpr(_rbexpr.over(rbexprs))
end

#pct_change(n: 1) ⇒ Expr

Computes percentage change between values.

Percentage change (as fraction) between current element and most-recent non-null element at least n period(s) before the current element.

Computes the change from the previous row by default.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [10, 11, 12, nil, 12]
  }
)
df.with_column(Polars.col("a").pct_change.alias("pct_change"))
# =>
# shape: (5, 2)
# ┌──────┬────────────┐
# │ a    ┆ pct_change │
# │ ---  ┆ ---        │
# │ i64  ┆ f64        │
# ╞══════╪════════════╡
# │ 10   ┆ null       │
# │ 11   ┆ 0.1        │
# │ 12   ┆ 0.090909   │
# │ null ┆ 0.0        │
# │ 12   ┆ 0.0        │
# └──────┴────────────┘

Parameters:

  • n (Integer) (defaults to: 1) —

    Periods to shift for forming percent change.

Returns:



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# File 'lib/polars/expr.rb', line 5896

def pct_change(n: 1)
  n = Utils.parse_into_expression(n)
  _from_rbexpr(_rbexpr.pct_change(n))
end

#peak_max ⇒ Expr

Get a boolean mask of the local maximum peaks.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3, 4, 5]})
df.select(Polars.col("a").peak_max)
# =>
# shape: (5, 1)
# ┌───────┐
# │ a     │
# │ ---   │
# │ bool  │
# ╞═══════╡
# │ false │
# │ false │
# │ false │
# │ false │
# │ true  │
# └───────┘

Returns:



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# File 'lib/polars/expr.rb', line 2482

def peak_max
  _from_rbexpr(_rbexpr.peak_max)
end

#peak_min ⇒ Expr

Get a boolean mask of the local minimum peaks.

Examples:

df = Polars::DataFrame.new({"a" => [4, 1, 3, 2, 5]})
df.select(Polars.col("a").peak_min)
# =>
# shape: (5, 1)
# ┌───────┐
# │ a     │
# │ ---   │
# │ bool  │
# ╞═══════╡
# │ false │
# │ true  │
# │ false │
# │ true  │
# │ false │
# └───────┘

Returns:



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# File 'lib/polars/expr.rb', line 2506

def peak_min
  _from_rbexpr(_rbexpr.peak_min)
end

#pow(exponent) ⇒ Expr

Raise expression to the power of exponent.

Examples:

df = Polars::DataFrame.new({"x" => [1, 2, 4, 8]})
df.with_columns(
  Polars.col("x").pow(3).alias("cube"),
  Polars.col("x").pow(Polars.col("x").log(2)).alias("x ** xlog2")
)
# =>
# shape: (4, 3)
# ┌─────┬──────┬────────────┐
# │ x   ┆ cube ┆ x ** xlog2 │
# │ --- ┆ ---  ┆ ---        │
# │ i64 ┆ i64  ┆ f64        │
# ╞═════╪══════╪════════════╡
# │ 1   ┆ 1    ┆ 1.0        │
# │ 2   ┆ 8    ┆ 2.0        │
# │ 4   ┆ 64   ┆ 16.0       │
# │ 8   ┆ 512  ┆ 512.0      │
# └─────┴──────┴────────────┘

Returns:



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# File 'lib/polars/expr.rb', line 3679

def pow(exponent)
  self**exponent
end

#prefix(prefix) ⇒ Expr

Add a prefix to the root column name of the expression.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, 3],
    "b" => ["x", "y", "z"]
  }
)
df.with_columns(Polars.all.reverse.name.prefix("reverse_"))
# =>
# shape: (3, 4)
# ┌─────┬─────┬───────────┬───────────┐
# │ a   ┆ b   ┆ reverse_a ┆ reverse_b │
# │ --- ┆ --- ┆ ---       ┆ ---       │
# │ i64 ┆ str ┆ i64       ┆ str       │
# ╞═════╪═════╪═══════════╪═══════════╡
# │ 1   ┆ x   ┆ 3         ┆ z         │
# │ 2   ┆ y   ┆ 2         ┆ y         │
# │ 3   ┆ z   ┆ 1         ┆ x         │
# └─────┴─────┴───────────┴───────────┘

Returns:



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# File 'lib/polars/expr.rb', line 434

def prefix(prefix)
  name.prefix(prefix)
end

#product ⇒ Expr

Compute the product of an expression.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3]})
df.select(Polars.col("a").product)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 6   │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2145

def product
  _from_rbexpr(_rbexpr.product)
end

#qcut(quantiles, labels: nil, left_closed: false, allow_duplicates: false, include_breaks: false) ⇒ Expr

Bin continuous values into discrete categories based on their quantiles.

Examples:

Divide a column into three categories according to pre-defined quantile probabilities.

df = Polars::DataFrame.new({"foo" => [-2, -1, 0, 1, 2]})
df.with_columns(
  Polars.col("foo").qcut([0.25, 0.75], labels: ["a", "b", "c"]).alias("qcut")
)
# =>
# shape: (5, 2)
# ┌─────┬──────┐
# │ foo ┆ qcut │
# │ --- ┆ ---  │
# │ i64 ┆ cat  │
# ╞═════╪══════╡
# │ -2  ┆ a    │
# │ -1  ┆ a    │
# │ 0   ┆ b    │
# │ 1   ┆ b    │
# │ 2   ┆ c    │
# └─────┴──────┘

Divide a column into two categories using uniform quantile probabilities.

df.with_columns(
  Polars.col("foo")
    .qcut(2, labels: ["low", "high"], left_closed: true)
    .alias("qcut")
)
# =>
# shape: (5, 2)
# ┌─────┬──────┐
# │ foo ┆ qcut │
# │ --- ┆ ---  │
# │ i64 ┆ cat  │
# ╞═════╪══════╡
# │ -2  ┆ low  │
# │ -1  ┆ low  │
# │ 0   ┆ high │
# │ 1   ┆ high │
# │ 2   ┆ high │
# └─────┴──────┘

Add both the category and the breakpoint.

df.with_columns(
  Polars.col("foo").qcut([0.25, 0.75], include_breaks: true).alias("qcut")
).unnest("qcut")
# =>
# shape: (5, 3)
# ┌─────┬────────────┬────────────┐
# │ foo ┆ breakpoint ┆ category   │
# │ --- ┆ ---        ┆ ---        │
# │ i64 ┆ f64        ┆ cat        │
# ╞═════╪════════════╪════════════╡
# │ -2  ┆ -1.0       ┆ (-inf, -1] │
# │ -1  ┆ -1.0       ┆ (-inf, -1] │
# │ 0   ┆ 1.0        ┆ (-1, 1]    │
# │ 1   ┆ 1.0        ┆ (-1, 1]    │
# │ 2   ┆ inf        ┆ (1, inf]   │
# └─────┴────────────┴────────────┘

Parameters:

  • quantiles (Array) —

    Either a list of quantile probabilities between 0 and 1 or a positive integer determining the number of bins with uniform probability.

  • labels (Array) (defaults to: nil) —

    Names of the categories. The number of labels must be equal to the number of categories.

  • left_closed (Boolean) (defaults to: false) —

    Set the intervals to be left-closed instead of right-closed.

  • allow_duplicates (Boolean) (defaults to: false) —

    If set to true, duplicates in the resulting quantiles are dropped, rather than raising a DuplicateError. This can happen even with unique probabilities, depending on the data.

  • include_breaks (Boolean) (defaults to: false) —

    Include a column with the right endpoint of the bin each observation falls in. This will change the data type of the output from a Categorical to a Struct.

Returns:



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# File 'lib/polars/expr.rb', line 2717

def qcut(quantiles, labels: nil, left_closed: false, allow_duplicates: false, include_breaks: false)
  if quantiles.is_a?(Integer)
    rbexpr = _rbexpr.qcut_uniform(
      quantiles, labels, left_closed, allow_duplicates, include_breaks
    )
  else
    rbexpr = _rbexpr.qcut(
      quantiles, labels, left_closed, allow_duplicates, include_breaks
    )
  end

  _from_rbexpr(rbexpr)
end

#quantile(quantile, interpolation: "nearest") ⇒ Expr

Get quantile value.

Examples:

df = Polars::DataFrame.new({"a" => [0, 1, 2, 3, 4, 5]})
df.select(Polars.col("a").quantile(0.3))
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 2.0 │
# └─────┘
df.select(Polars.col("a").quantile(0.3, interpolation: "higher"))
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 2.0 │
# └─────┘
df.select(Polars.col("a").quantile(0.3, interpolation: "lower"))
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 1.0 │
# └─────┘
df.select(Polars.col("a").quantile(0.3, interpolation: "midpoint"))
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 1.5 │
# └─────┘
df.select(Polars.col("a").quantile(0.3, interpolation: "linear"))
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 1.5 │
# └─────┘

Parameters:

  • quantile (Float) —

    Quantile between 0.0 and 1.0.

  • interpolation ("nearest", "higher", "lower", "midpoint", "linear") (defaults to: "nearest") —

    Interpolation method.

Returns:



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# File 'lib/polars/expr.rb', line 2579

def quantile(quantile, interpolation: "nearest")
  quantile = Utils.parse_into_expression(quantile, str_as_lit: false)
  _from_rbexpr(_rbexpr.quantile(quantile, interpolation))
end

#rank(method: "average", reverse: false, seed: nil) ⇒ Expr

Assign ranks to data, dealing with ties appropriately.

Examples:

The 'average' method:

df = Polars::DataFrame.new({"a" => [3, 6, 1, 1, 6]})
df.select(Polars.col("a").rank)
# =>
# shape: (5, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 3.0 │
# │ 4.5 │
# │ 1.5 │
# │ 1.5 │
# │ 4.5 │
# └─────┘

The 'ordinal' method:

df = Polars::DataFrame.new({"a" => [3, 6, 1, 1, 6]})
df.select(Polars.col("a").rank(method: "ordinal"))
# =>
# shape: (5, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ u32 │
# ╞═════╡
# │ 3   │
# │ 4   │
# │ 1   │
# │ 2   │
# │ 5   │
# └─────┘

Parameters:

  • method ("average", "min", "max", "dense", "ordinal", "random") (defaults to: "average") —

    The method used to assign ranks to tied elements. The following methods are available:

    • 'average' : The average of the ranks that would have been assigned to all the tied values is assigned to each value.
    • 'min' : The minimum of the ranks that would have been assigned to all the tied values is assigned to each value. (This is also referred to as "competition" ranking.)
    • 'max' : The maximum of the ranks that would have been assigned to all the tied values is assigned to each value.
    • 'dense' : Like 'min', but the rank of the next highest element is assigned the rank immediately after those assigned to the tied elements.
    • 'ordinal' : All values are given a distinct rank, corresponding to the order that the values occur in the Series.
    • 'random' : Like 'ordinal', but the rank for ties is not dependent on the order that the values occur in the Series.
  • reverse (Boolean) (defaults to: false) —

    Reverse the operation.

  • seed (Integer) (defaults to: nil) —

    If method: "random", use this as seed.

Returns:



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# File 'lib/polars/expr.rb', line 5829

def rank(method: "average", reverse: false, seed: nil)
  _from_rbexpr(_rbexpr.rank(method, reverse, seed))
end

#rechunk ⇒ Expr

Create a single chunk of memory for this Series.

Examples:

Create a Series with 3 nulls, append column a then rechunk

df = Polars::DataFrame.new({"a" => [1, 1, 2]})
df.select(Polars.repeat(nil, 3).append(Polars.col("a")).rechunk)
# =>
# shape: (6, 1)
# ┌────────┐
# │ repeat │
# │ ---    │
# │ i64    │
# ╞════════╡
# │ null   │
# │ null   │
# │ null   │
# │ 1      │
# │ 1      │
# │ 2      │
# └────────┘

Returns:



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# File 'lib/polars/expr.rb', line 879

def rechunk
  _from_rbexpr(_rbexpr.rechunk)
end

#reinterpret(signed: false) ⇒ Expr

Reinterpret the underlying bits as a signed/unsigned integer.

This operation is only allowed for 64bit integers. For lower bits integers, you can safely use that cast operation.

Examples:

s = Polars::Series.new("a", [1, 1, 2], dtype: :u64)
df = Polars::DataFrame.new([s])
df.select(
  [
    Polars.col("a").reinterpret(signed: true).alias("reinterpreted"),
    Polars.col("a").alias("original")
  ]
)
# =>
# shape: (3, 2)
# ┌───────────────┬──────────┐
# │ reinterpreted ┆ original │
# │ ---           ┆ ---      │
# │ i64           ┆ u64      │
# ╞═══════════════╪══════════╡
# │ 1             ┆ 1        │
# │ 1             ┆ 1        │
# │ 2             ┆ 2        │
# └───────────────┴──────────┘

Parameters:

  • signed (Boolean) (defaults to: false) —

    If true, reinterpret as :i64. Otherwise, reinterpret as :u64.

Returns:



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# File 'lib/polars/expr.rb', line 3930

def reinterpret(signed: false)
  _from_rbexpr(_rbexpr.reinterpret(signed))
end

#repeat_by(by) ⇒ Expr

Repeat the elements in this Series as specified in the given expression.

The repeated elements are expanded into a List.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => ["x", "y", "z"],
    "n" => [1, 2, 3]
  }
)
df.select(Polars.col("a").repeat_by("n"))
# =>
# shape: (3, 1)
# ┌─────────────────┐
# │ a               │
# │ ---             │
# │ list[str]       │
# ╞═════════════════╡
# │ ["x"]           │
# │ ["y", "y"]      │
# │ ["z", "z", "z"] │
# └─────────────────┘

Parameters:

  • by (Object) —

    Numeric column that determines how often the values will be repeated. The column will be coerced to UInt32. Give this dtype to make the coercion a no-op.

Returns:



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# File 'lib/polars/expr.rb', line 3778

def repeat_by(by)
  by = Utils.parse_into_expression(by, str_as_lit: false)
  _from_rbexpr(_rbexpr.repeat_by(by))
end

#replace(old, new = NO_DEFAULT, default: NO_DEFAULT, return_dtype: nil) ⇒ Expr

Replace values by different values.

Examples:

Replace a single value by another value. Values that were not replaced remain unchanged.

df = Polars::DataFrame.new({"a" => [1, 2, 2, 3]})
df.with_columns(replaced: Polars.col("a").replace(2, 100))
# =>
# shape: (4, 2)
# ┌─────┬──────────┐
# │ a   ┆ replaced │
# │ --- ┆ ---      │
# │ i64 ┆ i64      │
# ╞═════╪══════════╡
# │ 1   ┆ 1        │
# │ 2   ┆ 100      │
# │ 2   ┆ 100      │
# │ 3   ┆ 3        │
# └─────┴──────────┘

Replace multiple values by passing sequences to the old and new parameters.

df.with_columns(replaced: Polars.col("a").replace([2, 3], [100, 200]))
# =>
# shape: (4, 2)
# ┌─────┬──────────┐
# │ a   ┆ replaced │
# │ --- ┆ ---      │
# │ i64 ┆ i64      │
# ╞═════╪══════════╡
# │ 1   ┆ 1        │
# │ 2   ┆ 100      │
# │ 2   ┆ 100      │
# │ 3   ┆ 200      │
# └─────┴──────────┘

Passing a mapping with replacements is also supported as syntactic sugar. Specify a default to set all values that were not matched.

mapping = {2 => 100, 3 => 200}
df.with_columns(replaced: Polars.col("a").replace(mapping, default: -1))
# =>
# shape: (4, 2)
# ┌─────┬──────────┐
# │ a   ┆ replaced │
# │ --- ┆ ---      │
# │ i64 ┆ i64      │
# ╞═════╪══════════╡
# │ 1   ┆ -1       │
# │ 2   ┆ 100      │
# │ 2   ┆ 100      │
# │ 3   ┆ 200      │
# └─────┴──────────┘

Replacing by values of a different data type sets the return type based on a combination of the new data type and either the original data type or the default data type if it was set.

df = Polars::DataFrame.new({"a" => ["x", "y", "z"]})
mapping = {"x" => 1, "y" => 2, "z" => 3}
df.with_columns(replaced: Polars.col("a").replace(mapping))
# =>
# shape: (3, 2)
# ┌─────┬──────────┐
# │ a   ┆ replaced │
# │ --- ┆ ---      │
# │ str ┆ str      │
# ╞═════╪══════════╡
# │ x   ┆ 1        │
# │ y   ┆ 2        │
# │ z   ┆ 3        │
# └─────┴──────────┘
df.with_columns(replaced: Polars.col("a").replace(mapping, default: nil))
# =>
# shape: (3, 2)
# ┌─────┬──────────┐
# │ a   ┆ replaced │
# │ --- ┆ ---      │
# │ str ┆ i64      │
# ╞═════╪══════════╡
# │ x   ┆ 1        │
# │ y   ┆ 2        │
# │ z   ┆ 3        │
# └─────┴──────────┘

Set the return_dtype parameter to control the resulting data type directly.

df.with_columns(
  replaced: Polars.col("a").replace(mapping, return_dtype: Polars::UInt8)
)
# =>
# shape: (3, 2)
# ┌─────┬──────────┐
# │ a   ┆ replaced │
# │ --- ┆ ---      │
# │ str ┆ u8       │
# ╞═════╪══════════╡
# │ x   ┆ 1        │
# │ y   ┆ 2        │
# │ z   ┆ 3        │
# └─────┴──────────┘

Expression input is supported for all parameters.

df = Polars::DataFrame.new({"a" => [1, 2, 2, 3], "b" => [1.5, 2.5, 5.0, 1.0]})
df.with_columns(
  replaced: Polars.col("a").replace(
    Polars.col("a").max,
    Polars.col("b").sum,
    default: Polars.col("b")
  )
)
# =>
# shape: (4, 3)
# ┌─────┬─────┬──────────┐
# │ a   ┆ b   ┆ replaced │
# │ --- ┆ --- ┆ ---      │
# │ i64 ┆ f64 ┆ f64      │
# ╞═════╪═════╪══════════╡
# │ 1   ┆ 1.5 ┆ 1.5      │
# │ 2   ┆ 2.5 ┆ 2.5      │
# │ 2   ┆ 5.0 ┆ 5.0      │
# │ 3   ┆ 1.0 ┆ 10.0     │
# └─────┴─────┴──────────┘

Parameters:

  • old (Object) —

    Value or sequence of values to replace. Accepts expression input. Sequences are parsed as Series, other non-expression inputs are parsed as literals. Also accepts a mapping of values to their replacement.

  • new (Object) (defaults to: NO_DEFAULT) —

    Value or sequence of values to replace by. Accepts expression input. Sequences are parsed as Series, other non-expression inputs are parsed as literals. Length must match the length of old or have length 1.

  • default (Object) (defaults to: NO_DEFAULT) —

    Set values that were not replaced to this value. Defaults to keeping the original value. Accepts expression input. Non-expression inputs are parsed as literals.

  • return_dtype (Object) (defaults to: nil) —

    The data type of the resulting expression. If set to nil (default), the data type is determined automatically based on the other inputs.

Returns:



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# File 'lib/polars/expr.rb', line 7053

def replace(old, new = NO_DEFAULT, default: NO_DEFAULT, return_dtype: nil)
  if !default.eql?(NO_DEFAULT)
    return replace_strict(old, new, default: default, return_dtype: return_dtype)
  end

  if new.eql?(NO_DEFAULT) && old.is_a?(Hash)
    new = Series.new(old.values)
    old = Series.new(old.keys)
  else
    if old.is_a?(::Array)
      old = Series.new(old)
    end
    if new.is_a?(::Array)
      new = Series.new(new)
    end
  end

  old = Utils.parse_into_expression(old, str_as_lit: true)
  new = Utils.parse_into_expression(new, str_as_lit: true)

  result = _from_rbexpr(_rbexpr.replace(old, new))

  if !return_dtype.nil?
    result = result.cast(return_dtype)
  end

  result
end

#replace_strict(old, new = NO_DEFAULT, default: NO_DEFAULT, return_dtype: nil) ⇒ Expr

Note:

The global string cache must be enabled when replacing categorical values.

Replace all values by different values.

Examples:

Replace values by passing sequences to the old and new parameters.

df = Polars::DataFrame.new({"a" => [1, 2, 2, 3]})
df.with_columns(
  replaced: Polars.col("a").replace_strict([1, 2, 3], [100, 200, 300])
)
# =>
# shape: (4, 2)
# ┌─────┬──────────┐
# │ a   ┆ replaced │
# │ --- ┆ ---      │
# │ i64 ┆ i64      │
# ╞═════╪══════════╡
# │ 1   ┆ 100      │
# │ 2   ┆ 200      │
# │ 2   ┆ 200      │
# │ 3   ┆ 300      │
# └─────┴──────────┘

By default, an error is raised if any non-null values were not replaced. Specify a default to set all values that were not matched.

mapping = {2 => 200, 3 => 300}
df.with_columns(replaced: Polars.col("a").replace_strict(mapping, default: -1))
# =>
# shape: (4, 2)
# ┌─────┬──────────┐
# │ a   ┆ replaced │
# │ --- ┆ ---      │
# │ i64 ┆ i64      │
# ╞═════╪══════════╡
# │ 1   ┆ -1       │
# │ 2   ┆ 200      │
# │ 2   ┆ 200      │
# │ 3   ┆ 300      │
# └─────┴──────────┘

Replacing by values of a different data type sets the return type based on a combination of the new data type and the default data type.

df = Polars::DataFrame.new({"a" => ["x", "y", "z"]})
mapping = {"x" => 1, "y" => 2, "z" => 3}
df.with_columns(replaced: Polars.col("a").replace_strict(mapping))
# =>
# shape: (3, 2)
# ┌─────┬──────────┐
# │ a   ┆ replaced │
# │ --- ┆ ---      │
# │ str ┆ i64      │
# ╞═════╪══════════╡
# │ x   ┆ 1        │
# │ y   ┆ 2        │
# │ z   ┆ 3        │
# └─────┴──────────┘
df.with_columns(replaced: Polars.col("a").replace_strict(mapping, default: "x"))
# =>
# shape: (3, 2)
# ┌─────┬──────────┐
# │ a   ┆ replaced │
# │ --- ┆ ---      │
# │ str ┆ str      │
# ╞═════╪══════════╡
# │ x   ┆ 1        │
# │ y   ┆ 2        │
# │ z   ┆ 3        │
# └─────┴──────────┘

Set the return_dtype parameter to control the resulting data type directly.

df.with_columns(
  replaced: Polars.col("a").replace_strict(mapping, return_dtype: Polars::UInt8)
)
# =>
# shape: (3, 2)
# ┌─────┬──────────┐
# │ a   ┆ replaced │
# │ --- ┆ ---      │
# │ str ┆ u8       │
# ╞═════╪══════════╡
# │ x   ┆ 1        │
# │ y   ┆ 2        │
# │ z   ┆ 3        │
# └─────┴──────────┘

Expression input is supported for all parameters.

df = Polars::DataFrame.new({"a" => [1, 2, 2, 3], "b" => [1.5, 2.5, 5.0, 1.0]})
df.with_columns(
  replaced: Polars.col("a").replace_strict(
    Polars.col("a").max,
    Polars.col("b").sum,
    default: Polars.col("b")
  )
)
# =>
# shape: (4, 3)
# ┌─────┬─────┬──────────┐
# │ a   ┆ b   ┆ replaced │
# │ --- ┆ --- ┆ ---      │
# │ i64 ┆ f64 ┆ f64      │
# ╞═════╪═════╪══════════╡
# │ 1   ┆ 1.5 ┆ 1.5      │
# │ 2   ┆ 2.5 ┆ 2.5      │
# │ 2   ┆ 5.0 ┆ 5.0      │
# │ 3   ┆ 1.0 ┆ 10.0     │
# └─────┴─────┴──────────┘

Parameters:

  • old (Object) —

    Value or sequence of values to replace. Accepts expression input. Sequences are parsed as Series, other non-expression inputs are parsed as literals. Also accepts a mapping of values to their replacement as syntactic sugar for replace_all(old: Series.new(mapping.keys), new: Serie.new(mapping.values)).

  • new (Object) (defaults to: NO_DEFAULT) —

    Value or sequence of values to replace by. Accepts expression input. Sequences are parsed as Series, other non-expression inputs are parsed as literals. Length must match the length of old or have length 1.

  • default (Object) (defaults to: NO_DEFAULT) —

    Set values that were not replaced to this value. If no default is specified, (default), an error is raised if any values were not replaced. Accepts expression input. Non-expression inputs are parsed as literals.

  • return_dtype (Object) (defaults to: nil) —

    The data type of the resulting expression. If set to nil (default), the data type is determined automatically based on the other inputs.

Returns:



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# File 'lib/polars/expr.rb', line 7209

def replace_strict(
  old,
  new = NO_DEFAULT,
  default: NO_DEFAULT,
  return_dtype: nil
)
  if new.eql?(NO_DEFAULT) && old.is_a?(Hash)
    new = Series.new(old.values)
    old = Series.new(old.keys)
  end

  old = Utils.parse_into_expression(old, str_as_lit: true, list_as_series: true)
  new = Utils.parse_into_expression(new, str_as_lit: true, list_as_series: true)

  default = default.eql?(NO_DEFAULT) ? nil : Utils.parse_into_expression(default, str_as_lit: true)

  _from_rbexpr(
    _rbexpr.replace_strict(old, new, default, return_dtype)
  )
end

#reshape(dims) ⇒ Expr

Reshape this Expr to a flat Series or a Series of Lists.

Examples:

df = Polars::DataFrame.new({"foo" => [1, 2, 3, 4, 5, 6, 7, 8, 9]})
square = df.select(Polars.col("foo").reshape([3, 3]))
# =>
# shape: (3, 1)
# ┌───────────────┐
# │ foo           │
# │ ---           │
# │ array[i64, 3] │
# ╞═══════════════╡
# │ [1, 2, 3]     │
# │ [4, 5, 6]     │
# │ [7, 8, 9]     │
# └───────────────┘
square.select(Polars.col("foo").reshape([9]))
# =>
# shape: (9, 1)
# ┌─────┐
# │ foo │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 1   │
# │ 2   │
# │ 3   │
# │ 4   │
# │ 5   │
# │ 6   │
# │ 7   │
# │ 8   │
# │ 9   │
# └─────┘

Parameters:

  • dims (Array) —

    Tuple of the dimension sizes. If a -1 is used in any of the dimensions, that dimension is inferred.

Returns:



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# File 'lib/polars/expr.rb', line 6413

def reshape(dims)
  _from_rbexpr(_rbexpr.reshape(dims))
end

#reverse ⇒ Expr

Reverse the selection.

Examples:

df = Polars::DataFrame.new(
  {
    "A" => [1, 2, 3, 4, 5],
    "fruits" => ["banana", "banana", "apple", "apple", "banana"],
    "B" => [5, 4, 3, 2, 1],
    "cars" => ["beetle", "audi", "beetle", "beetle", "beetle"]
  }
)
df.select(
  [
    Polars.all,
    Polars.all.reverse.name.suffix("_reverse")
  ]
)
# =>
# shape: (5, 8)
# ┌─────┬────────┬─────┬────────┬───────────┬────────────────┬───────────┬──────────────┐
# │ A   ┆ fruits ┆ B   ┆ cars   ┆ A_reverse ┆ fruits_reverse ┆ B_reverse ┆ cars_reverse │
# │ --- ┆ ---    ┆ --- ┆ ---    ┆ ---       ┆ ---            ┆ ---       ┆ ---          │
# │ i64 ┆ str    ┆ i64 ┆ str    ┆ i64       ┆ str            ┆ i64       ┆ str          │
# ╞═════╪════════╪═════╪════════╪═══════════╪════════════════╪═══════════╪══════════════╡
# │ 1   ┆ banana ┆ 5   ┆ beetle ┆ 5         ┆ banana         ┆ 1         ┆ beetle       │
# │ 2   ┆ banana ┆ 4   ┆ audi   ┆ 4         ┆ apple          ┆ 2         ┆ beetle       │
# │ 3   ┆ apple  ┆ 3   ┆ beetle ┆ 3         ┆ apple          ┆ 3         ┆ beetle       │
# │ 4   ┆ apple  ┆ 2   ┆ beetle ┆ 2         ┆ banana         ┆ 4         ┆ audi         │
# │ 5   ┆ banana ┆ 1   ┆ beetle ┆ 1         ┆ banana         ┆ 5         ┆ beetle       │
# └─────┴────────┴─────┴────────┴───────────┴────────────────┴───────────┴──────────────┘

Returns:



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# File 'lib/polars/expr.rb', line 1935

def reverse
  _from_rbexpr(_rbexpr.reverse)
end

#rle ⇒ Expr

Get the lengths of runs of identical values.

Examples:

df = Polars::DataFrame.new(Polars::Series.new("s", [1, 1, 2, 1, nil, 1, 3, 3]))
df.select(Polars.col("s").rle).unnest("s")
# =>
# shape: (6, 2)
# ┌─────┬───────┐
# │ len ┆ value │
# │ --- ┆ ---   │
# │ u32 ┆ i64   │
# ╞═════╪═══════╡
# │ 2   ┆ 1     │
# │ 1   ┆ 2     │
# │ 1   ┆ 1     │
# │ 1   ┆ null  │
# │ 1   ┆ 1     │
# │ 2   ┆ 3     │
# └─────┴───────┘

Returns:



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# File 'lib/polars/expr.rb', line 2752

def rle
  _from_rbexpr(_rbexpr.rle)
end

#rle_id ⇒ Expr

Map values to run IDs.

Similar to RLE, but it maps each value to an ID corresponding to the run into which it falls. This is especially useful when you want to define groups by runs of identical values rather than the values themselves.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 1, 1, 1], "b" => ["x", "x", nil, "y", "y"]})
df.with_columns([Polars.col("a").rle_id.alias("a_r"), Polars.struct(["a", "b"]).rle_id.alias("ab_r")])
# =>
# shape: (5, 4)
# ┌─────┬──────┬─────┬──────┐
# │ a   ┆ b    ┆ a_r ┆ ab_r │
# │ --- ┆ ---  ┆ --- ┆ ---  │
# │ i64 ┆ str  ┆ u32 ┆ u32  │
# ╞═════╪══════╪═════╪══════╡
# │ 1   ┆ x    ┆ 0   ┆ 0    │
# │ 2   ┆ x    ┆ 1   ┆ 1    │
# │ 1   ┆ null ┆ 2   ┆ 2    │
# │ 1   ┆ y    ┆ 2   ┆ 3    │
# │ 1   ┆ y    ┆ 2   ┆ 3    │
# └─────┴──────┴─────┴──────┘

Returns:



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# File 'lib/polars/expr.rb', line 2780

def rle_id
  _from_rbexpr(_rbexpr.rle_id)
end

#rolling_max(window_size, weights: nil, min_periods: nil, center: false) ⇒ Expr

Note:

This functionality is experimental and may change without it being considered a breaking change.

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using group_by_rolling this method can cache the window size computation.

Apply a rolling max (moving max) over the values in this array.

A window of length window_size will traverse the array. The values that fill this window will (optionally) be multiplied with the weights given by the weight vector. The resulting values will be aggregated to their sum.

Examples:

df = Polars::DataFrame.new({"A" => [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]})
df.select(
  [
    Polars.col("A").rolling_max(2)
  ]
)
# =>
# shape: (6, 1)
# ┌──────┐
# │ A    │
# │ ---  │
# │ f64  │
# ╞══════╡
# │ null │
# │ 2.0  │
# │ 3.0  │
# │ 4.0  │
# │ 5.0  │
# │ 6.0  │
# └──────┘

Parameters:

  • window_size (Integer) —

    The length of the window. Can be a fixed integer size, or a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 day)
    • 1w (1 week)
    • 1mo (1 calendar month)
    • 1y (1 calendar year)
    • 1i (1 index count)

    If a timedelta or the dynamic string language is used, the by and closed arguments must also be set.

  • weights (Array) (defaults to: nil) —

    An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.

  • min_periods (Integer) (defaults to: nil) —

    The number of values in the window that should be non-null before computing a result. If None, it will be set equal to window size.

  • center (Boolean) (defaults to: false) —

    Set the labels at the center of the window

Returns:



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# File 'lib/polars/expr.rb', line 5136

def rolling_max(
  window_size,
  weights: nil,
  min_periods: nil,
  center: false
)
  _from_rbexpr(
    _rbexpr.rolling_max(
      window_size, weights, min_periods, center
    )
  )
end

#rolling_max_by(by, window_size, min_periods: 1, closed: "right", warn_if_unsorted: nil) ⇒ Expr

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using rolling - this method can cache the window size computation.

Apply a rolling max based on another column.

Examples:

Create a DataFrame with a datetime column and a row number column

start = DateTime.new(2001, 1, 1)
stop = DateTime.new(2001, 1, 2)
df_temporal = Polars::DataFrame.new(
    {"date" => Polars.datetime_range(start, stop, "1h", eager: true)}
).with_row_index
# =>
# shape: (25, 2)
# ┌───────┬─────────────────────┐
# │ index ┆ date                │
# │ ---   ┆ ---                 │
# │ u32   ┆ datetime[ns]        │
# ╞═══════╪═════════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 │
# │ 1     ┆ 2001-01-01 01:00:00 │
# │ 2     ┆ 2001-01-01 02:00:00 │
# │ 3     ┆ 2001-01-01 03:00:00 │
# │ 4     ┆ 2001-01-01 04:00:00 │
# │ …     ┆ …                   │
# │ 20    ┆ 2001-01-01 20:00:00 │
# │ 21    ┆ 2001-01-01 21:00:00 │
# │ 22    ┆ 2001-01-01 22:00:00 │
# │ 23    ┆ 2001-01-01 23:00:00 │
# │ 24    ┆ 2001-01-02 00:00:00 │
# └───────┴─────────────────────┘

Compute the rolling max with the temporal windows closed on the right (default)

df_temporal.with_columns(
  rolling_row_max: Polars.col("index").rolling_max_by("date", "2h")
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬─────────────────┐
# │ index ┆ date                ┆ rolling_row_max │
# │ ---   ┆ ---                 ┆ ---             │
# │ u32   ┆ datetime[ns]        ┆ u32             │
# ╞═══════╪═════════════════════╪═════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ 0               │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 1               │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 2               │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 3               │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 4               │
# │ …     ┆ …                   ┆ …               │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 20              │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 21              │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 22              │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 23              │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 24              │
# └───────┴─────────────────────┴─────────────────┘

Compute the rolling max with the closure of windows on both sides

df_temporal.with_columns(
  rolling_row_max: Polars.col("index").rolling_max_by(
    "date", "2h", closed: "both"
  )
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬─────────────────┐
# │ index ┆ date                ┆ rolling_row_max │
# │ ---   ┆ ---                 ┆ ---             │
# │ u32   ┆ datetime[ns]        ┆ u32             │
# ╞═══════╪═════════════════════╪═════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ 0               │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 1               │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 2               │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 3               │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 4               │
# │ …     ┆ …                   ┆ …               │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 20              │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 21              │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 22              │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 23              │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 24              │
# └───────┴─────────────────────┴─────────────────┘

Parameters:

  • by (String) —

    This column must be of dtype Datetime or Date.

  • window_size (String) —

    The length of the window. Can be a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 calendar day)
    • 1w (1 calendar week)
    • 1mo (1 calendar month)
    • 1q (1 calendar quarter)
    • 1y (1 calendar year)

    By "calendar day", we mean the corresponding time on the next day (which may not be 24 hours, due to daylight savings). Similarly for "calendar week", "calendar month", "calendar quarter", and "calendar year".

  • min_periods (Integer) (defaults to: 1) —

    The number of values in the window that should be non-null before computing a result.

  • closed ('left', 'right', 'both', 'none') (defaults to: "right") —

    Define which sides of the temporal interval are closed (inclusive), defaults to 'right'.

  • warn_if_unsorted (Boolean) (defaults to: nil) —

    Warn if data is not known to be sorted by by column.

Returns:



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# File 'lib/polars/expr.rb', line 4215

def rolling_max_by(
  by,
  window_size,
  min_periods: 1,
  closed: "right",
  warn_if_unsorted: nil
)
  window_size = _prepare_rolling_by_window_args(window_size)
  by = Utils.parse_into_expression(by)
  _from_rbexpr(
    _rbexpr.rolling_max_by(by, window_size, min_periods, closed)
  )
end

#rolling_mean(window_size, weights: nil, min_periods: nil, center: false) ⇒ Expr

Note:

This functionality is experimental and may change without it being considered a breaking change.

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using group_by_rolling this method can cache the window size computation.

Apply a rolling mean (moving mean) over the values in this array.

A window of length window_size will traverse the array. The values that fill this window will (optionally) be multiplied with the weights given by the weight vector. The resulting values will be aggregated to their sum.

Examples:

df = Polars::DataFrame.new({"A" => [1.0, 8.0, 6.0, 2.0, 16.0, 10.0]})
df.select(
  [
    Polars.col("A").rolling_mean(2)
  ]
)
# =>
# shape: (6, 1)
# ┌──────┐
# │ A    │
# │ ---  │
# │ f64  │
# ╞══════╡
# │ null │
# │ 4.5  │
# │ 7.0  │
# │ 4.0  │
# │ 9.0  │
# │ 13.0 │
# └──────┘

Parameters:

  • window_size (Integer) —

    The length of the window. Can be a fixed integer size, or a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 day)
    • 1w (1 week)
    • 1mo (1 calendar month)
    • 1y (1 calendar year)
    • 1i (1 index count)

    If a timedelta or the dynamic string language is used, the by and closed arguments must also be set.

  • weights (Array) (defaults to: nil) —

    An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.

  • min_periods (Integer) (defaults to: nil) —

    The number of values in the window that should be non-null before computing a result. If None, it will be set equal to window size.

  • center (Boolean) (defaults to: false) —

    Set the labels at the center of the window

Returns:



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# File 'lib/polars/expr.rb', line 5214

def rolling_mean(
  window_size,
  weights: nil,
  min_periods: nil,
  center: false
)
  _from_rbexpr(
    _rbexpr.rolling_mean(
      window_size, weights, min_periods, center
    )
  )
end

#rolling_mean_by(by, window_size, min_periods: 1, closed: "right", warn_if_unsorted: nil) ⇒ Expr

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using rolling - this method can cache the window size computation.

Apply a rolling mean based on another column.

Examples:

Create a DataFrame with a datetime column and a row number column

start = DateTime.new(2001, 1, 1)
stop = DateTime.new(2001, 1, 2)
df_temporal = Polars::DataFrame.new(
    {"date" => Polars.datetime_range(start, stop, "1h", eager: true)}
).with_row_index
# =>
# shape: (25, 2)
# ┌───────┬─────────────────────┐
# │ index ┆ date                │
# │ ---   ┆ ---                 │
# │ u32   ┆ datetime[ns]        │
# ╞═══════╪═════════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 │
# │ 1     ┆ 2001-01-01 01:00:00 │
# │ 2     ┆ 2001-01-01 02:00:00 │
# │ 3     ┆ 2001-01-01 03:00:00 │
# │ 4     ┆ 2001-01-01 04:00:00 │
# │ …     ┆ …                   │
# │ 20    ┆ 2001-01-01 20:00:00 │
# │ 21    ┆ 2001-01-01 21:00:00 │
# │ 22    ┆ 2001-01-01 22:00:00 │
# │ 23    ┆ 2001-01-01 23:00:00 │
# │ 24    ┆ 2001-01-02 00:00:00 │
# └───────┴─────────────────────┘

Compute the rolling mean with the temporal windows closed on the right (default)

df_temporal.with_columns(
  rolling_row_mean: Polars.col("index").rolling_mean_by(
    "date", "2h"
  )
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬──────────────────┐
# │ index ┆ date                ┆ rolling_row_mean │
# │ ---   ┆ ---                 ┆ ---              │
# │ u32   ┆ datetime[ns]        ┆ f64              │
# ╞═══════╪═════════════════════╪══════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ 0.0              │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 0.5              │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 1.5              │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 2.5              │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 3.5              │
# │ …     ┆ …                   ┆ …                │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 19.5             │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 20.5             │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 21.5             │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 22.5             │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 23.5             │
# └───────┴─────────────────────┴──────────────────┘

Compute the rolling mean with the closure of windows on both sides

df_temporal.with_columns(
  rolling_row_mean: Polars.col("index").rolling_mean_by(
    "date", "2h", closed: "both"
  )
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬──────────────────┐
# │ index ┆ date                ┆ rolling_row_mean │
# │ ---   ┆ ---                 ┆ ---              │
# │ u32   ┆ datetime[ns]        ┆ f64              │
# ╞═══════╪═════════════════════╪══════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ 0.0              │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 0.5              │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 1.0              │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 2.0              │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 3.0              │
# │ …     ┆ …                   ┆ …                │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 19.0             │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 20.0             │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 21.0             │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 22.0             │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 23.0             │
# └───────┴─────────────────────┴──────────────────┘

Parameters:

  • by (String) —

    This column must be of dtype Datetime or Date.

  • window_size (String) —

    The length of the window. Can be a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 calendar day)
    • 1w (1 calendar week)
    • 1mo (1 calendar month)
    • 1q (1 calendar quarter)
    • 1y (1 calendar year)

    By "calendar day", we mean the corresponding time on the next day (which may not be 24 hours, due to daylight savings). Similarly for "calendar week", "calendar month", "calendar quarter", and "calendar year".

  • min_periods (Integer) (defaults to: 1) —

    The number of values in the window that should be non-null before computing a result.

  • closed ('left', 'right', 'both', 'none') (defaults to: "right") —

    Define which sides of the temporal interval are closed (inclusive), defaults to 'right'.

  • warn_if_unsorted (Boolean) (defaults to: nil) —

    Warn if data is not known to be sorted by by column.

Returns:



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# File 'lib/polars/expr.rb', line 4346

def rolling_mean_by(
  by,
  window_size,
  min_periods: 1,
  closed: "right",
  warn_if_unsorted: nil
)
  window_size = _prepare_rolling_by_window_args(window_size)
  by = Utils.parse_into_expression(by)
  _from_rbexpr(
    _rbexpr.rolling_mean_by(
      by,
      window_size,
      min_periods,
      closed
    )
  )
end

#rolling_median(window_size, weights: nil, min_periods: nil, center: false) ⇒ Expr

Note:

This functionality is experimental and may change without it being considered a breaking change.

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using group_by_rolling this method can cache the window size computation.

Compute a rolling median.

Examples:

df = Polars::DataFrame.new({"A" => [1.0, 2.0, 3.0, 4.0, 6.0, 8.0]})
df.select(
  [
    Polars.col("A").rolling_median(3)
  ]
)
# =>
# shape: (6, 1)
# ┌──────┐
# │ A    │
# │ ---  │
# │ f64  │
# ╞══════╡
# │ null │
# │ null │
# │ 2.0  │
# │ 3.0  │
# │ 4.0  │
# │ 6.0  │
# └──────┘

Parameters:

  • window_size (Integer) —

    The length of the window. Can be a fixed integer size, or a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 day)
    • 1w (1 week)
    • 1mo (1 calendar month)
    • 1y (1 calendar year)
    • 1i (1 index count)

    If a timedelta or the dynamic string language is used, the by and closed arguments must also be set.

  • weights (Array) (defaults to: nil) —

    An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.

  • min_periods (Integer) (defaults to: nil) —

    The number of values in the window that should be non-null before computing a result. If None, it will be set equal to window size.

  • center (Boolean) (defaults to: false) —

    Set the labels at the center of the window

Returns:



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# File 'lib/polars/expr.rb', line 5524

def rolling_median(
  window_size,
  weights: nil,
  min_periods: nil,
  center: false
)
  _from_rbexpr(
    _rbexpr.rolling_median(
      window_size, weights, min_periods, center
    )
  )
end

#rolling_median_by(by, window_size, min_periods: 1, closed: "right", warn_if_unsorted: nil) ⇒ Expr

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using rolling - this method can cache the window size computation.

Compute a rolling median based on another column.

Examples:

Create a DataFrame with a datetime column and a row number column

start = DateTime.new(2001, 1, 1)
stop = DateTime.new(2001, 1, 2)
df_temporal = Polars::DataFrame.new(
  {"date" => Polars.datetime_range(start, stop, "1h", eager: true)}
).with_row_index
# =>
# shape: (25, 2)
# ┌───────┬─────────────────────┐
# │ index ┆ date                │
# │ ---   ┆ ---                 │
# │ u32   ┆ datetime[ns]        │
# ╞═══════╪═════════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 │
# │ 1     ┆ 2001-01-01 01:00:00 │
# │ 2     ┆ 2001-01-01 02:00:00 │
# │ 3     ┆ 2001-01-01 03:00:00 │
# │ 4     ┆ 2001-01-01 04:00:00 │
# │ …     ┆ …                   │
# │ 20    ┆ 2001-01-01 20:00:00 │
# │ 21    ┆ 2001-01-01 21:00:00 │
# │ 22    ┆ 2001-01-01 22:00:00 │
# │ 23    ┆ 2001-01-01 23:00:00 │
# │ 24    ┆ 2001-01-02 00:00:00 │
# └───────┴─────────────────────┘

Compute the rolling median with the temporal windows closed on the right:

df_temporal.with_columns(
  rolling_row_median: Polars.col("index").rolling_median_by(
    "date", "2h"
  )
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬────────────────────┐
# │ index ┆ date                ┆ rolling_row_median │
# │ ---   ┆ ---                 ┆ ---                │
# │ u32   ┆ datetime[ns]        ┆ f64                │
# ╞═══════╪═════════════════════╪════════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ 0.0                │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 0.5                │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 1.5                │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 2.5                │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 3.5                │
# │ …     ┆ …                   ┆ …                  │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 19.5               │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 20.5               │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 21.5               │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 22.5               │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 23.5               │
# └───────┴─────────────────────┴────────────────────┘

Parameters:

  • by (String) —

    This column must be of dtype Datetime or Date.

  • window_size (String) —

    The length of the window. Can be a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 calendar day)
    • 1w (1 calendar week)
    • 1mo (1 calendar month)
    • 1q (1 calendar quarter)
    • 1y (1 calendar year)

    By "calendar day", we mean the corresponding time on the next day (which may not be 24 hours, due to daylight savings). Similarly for "calendar week", "calendar month", "calendar quarter", and "calendar year".

  • min_periods (Integer) (defaults to: 1) —

    The number of values in the window that should be non-null before computing a result.

  • closed ('left', 'right', 'both', 'none') (defaults to: "right") —

    Define which sides of the temporal interval are closed (inclusive), defaults to 'right'.

  • warn_if_unsorted (Boolean) (defaults to: nil) —

    Warn if data is not known to be sorted by by column.

Returns:



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# File 'lib/polars/expr.rb', line 4861

def rolling_median_by(
  by,
  window_size,
  min_periods: 1,
  closed: "right",
  warn_if_unsorted: nil
)
  window_size = _prepare_rolling_by_window_args(window_size)
  by = Utils.parse_into_expression(by)
  _from_rbexpr(
    _rbexpr.rolling_median_by(by, window_size, min_periods, closed)
  )
end

#rolling_min(window_size, weights: nil, min_periods: nil, center: false) ⇒ Expr

Note:

This functionality is experimental and may change without it being considered a breaking change.

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using group_by_rolling this method can cache the window size computation.

Apply a rolling min (moving min) over the values in this array.

A window of length window_size will traverse the array. The values that fill this window will (optionally) be multiplied with the weights given by the weight vector. The resulting values will be aggregated to their sum.

Examples:

df = Polars::DataFrame.new({"A" => [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]})
df.select(
  [
    Polars.col("A").rolling_min(2)
  ]
)
# =>
# shape: (6, 1)
# ┌──────┐
# │ A    │
# │ ---  │
# │ f64  │
# ╞══════╡
# │ null │
# │ 1.0  │
# │ 2.0  │
# │ 3.0  │
# │ 4.0  │
# │ 5.0  │
# └──────┘

Parameters:

  • window_size (Integer) —

    The length of the window. Can be a fixed integer size, or a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 day)
    • 1w (1 week)
    • 1mo (1 calendar month)
    • 1y (1 calendar year)
    • 1i (1 index count)

    If a timedelta or the dynamic string language is used, the by and closed arguments must also be set.

  • weights (Array) (defaults to: nil) —

    An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.

  • min_periods (Integer) (defaults to: nil) —

    The number of values in the window that should be non-null before computing a result. If None, it will be set equal to window size.

  • center (Boolean) (defaults to: false) —

    Set the labels at the center of the window

Returns:



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# File 'lib/polars/expr.rb', line 5058

def rolling_min(
  window_size,
  weights: nil,
  min_periods: nil,
  center: false
)
  _from_rbexpr(
    _rbexpr.rolling_min(
      window_size, weights, min_periods, center
    )
  )
end

#rolling_min_by(by, window_size, min_periods: 1, closed: "right", warn_if_unsorted: nil) ⇒ Expr

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using rolling - this method can cache the window size computation.

Apply a rolling min based on another column.

Examples:

Create a DataFrame with a datetime column and a row number column

start = DateTime.new(2001, 1, 1)
stop = DateTime.new(2001, 1, 2)
df_temporal = Polars::DataFrame.new(
  {"date" => Polars.datetime_range(start, stop, "1h", eager: true)}
).with_row_index
# =>
# shape: (25, 2)
# ┌───────┬─────────────────────┐
# │ index ┆ date                │
# │ ---   ┆ ---                 │
# │ u32   ┆ datetime[ns]        │
# ╞═══════╪═════════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 │
# │ 1     ┆ 2001-01-01 01:00:00 │
# │ 2     ┆ 2001-01-01 02:00:00 │
# │ 3     ┆ 2001-01-01 03:00:00 │
# │ 4     ┆ 2001-01-01 04:00:00 │
# │ …     ┆ …                   │
# │ 20    ┆ 2001-01-01 20:00:00 │
# │ 21    ┆ 2001-01-01 21:00:00 │
# │ 22    ┆ 2001-01-01 22:00:00 │
# │ 23    ┆ 2001-01-01 23:00:00 │
# │ 24    ┆ 2001-01-02 00:00:00 │
# └───────┴─────────────────────┘

Compute the rolling min with the temporal windows closed on the right (default)

df_temporal.with_columns(
  rolling_row_min: Polars.col("index").rolling_min_by("date", "2h")
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬─────────────────┐
# │ index ┆ date                ┆ rolling_row_min │
# │ ---   ┆ ---                 ┆ ---             │
# │ u32   ┆ datetime[ns]        ┆ u32             │
# ╞═══════╪═════════════════════╪═════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ 0               │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 0               │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 1               │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 2               │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 3               │
# │ …     ┆ …                   ┆ …               │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 19              │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 20              │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 21              │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 22              │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 23              │
# └───────┴─────────────────────┴─────────────────┘

Parameters:

  • by (String) —

    This column must be of dtype Datetime or Date.

  • window_size (String) —

    The length of the window. Can be a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 calendar day)
    • 1w (1 calendar week)
    • 1mo (1 calendar month)
    • 1q (1 calendar quarter)
    • 1y (1 calendar year)

    By "calendar day", we mean the corresponding time on the next day (which may not be 24 hours, due to daylight savings). Similarly for "calendar week", "calendar month", "calendar quarter", and "calendar year".

  • min_periods (Integer) (defaults to: 1) —

    The number of values in the window that should be non-null before computing a result.

  • closed ('left', 'right', 'both', 'none') (defaults to: "right") —

    Define which sides of the temporal interval are closed (inclusive), defaults to 'right'.

  • warn_if_unsorted (Boolean) (defaults to: nil) —

    Warn if data is not known to be sorted by by column.

Returns:



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# File 'lib/polars/expr.rb', line 4086

def rolling_min_by(
  by,
  window_size,
  min_periods: 1,
  closed: "right",
  warn_if_unsorted: nil
)
  window_size = _prepare_rolling_by_window_args(window_size)
  by = Utils.parse_into_expression(by)
  _from_rbexpr(
    _rbexpr.rolling_min_by(by, window_size, min_periods, closed)
  )
end

#rolling_quantile(quantile, interpolation: "nearest", window_size: 2, weights: nil, min_periods: nil, center: false) ⇒ Expr

Note:

This functionality is experimental and may change without it being considered a breaking change.

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using group_by_rolling this method can cache the window size computation.

Compute a rolling quantile.

Examples:

df = Polars::DataFrame.new({"A" => [1.0, 2.0, 3.0, 4.0, 6.0, 8.0]})
df.select(
  [
    Polars.col("A").rolling_quantile(0.33, window_size: 3)
  ]
)
# =>
# shape: (6, 1)
# ┌──────┐
# │ A    │
# │ ---  │
# │ f64  │
# ╞══════╡
# │ null │
# │ null │
# │ 1.0  │
# │ 2.0  │
# │ 3.0  │
# │ 4.0  │
# └──────┘

Parameters:

  • quantile (Float) —

    Quantile between 0.0 and 1.0.

  • interpolation ("nearest", "higher", "lower", "midpoint", "linear") (defaults to: "nearest") —

    Interpolation method.

  • window_size (Integer) (defaults to: 2) —

    The length of the window. Can be a fixed integer size, or a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 day)
    • 1w (1 week)
    • 1mo (1 calendar month)
    • 1y (1 calendar year)
    • 1i (1 index count)

    If a timedelta or the dynamic string language is used, the by and closed arguments must also be set.

  • weights (Array) (defaults to: nil) —

    An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.

  • min_periods (Integer) (defaults to: nil) —

    The number of values in the window that should be non-null before computing a result. If None, it will be set equal to window size.

  • center (Boolean) (defaults to: false) —

    Set the labels at the center of the window

Returns:



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# File 'lib/polars/expr.rb', line 5602

def rolling_quantile(
  quantile,
  interpolation: "nearest",
  window_size: 2,
  weights: nil,
  min_periods: nil,
  center: false
)
  _from_rbexpr(
    _rbexpr.rolling_quantile(
      quantile, interpolation, window_size, weights, min_periods, center
    )
  )
end

#rolling_quantile_by(by, window_size, quantile:, interpolation: "nearest", min_periods: 1, closed: "right", warn_if_unsorted: nil) ⇒ Expr

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using rolling - this method can cache the window size computation.

Compute a rolling quantile based on another column.

Examples:

Create a DataFrame with a datetime column and a row number column

start = DateTime.new(2001, 1, 1)
stop = DateTime.new(2001, 1, 2)
df_temporal = Polars::DataFrame.new(
    {"date" => Polars.datetime_range(start, stop, "1h", eager: true)}
).with_row_index
# =>
# shape: (25, 2)
# ┌───────┬─────────────────────┐
# │ index ┆ date                │
# │ ---   ┆ ---                 │
# │ u32   ┆ datetime[ns]        │
# ╞═══════╪═════════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 │
# │ 1     ┆ 2001-01-01 01:00:00 │
# │ 2     ┆ 2001-01-01 02:00:00 │
# │ 3     ┆ 2001-01-01 03:00:00 │
# │ 4     ┆ 2001-01-01 04:00:00 │
# │ …     ┆ …                   │
# │ 20    ┆ 2001-01-01 20:00:00 │
# │ 21    ┆ 2001-01-01 21:00:00 │
# │ 22    ┆ 2001-01-01 22:00:00 │
# │ 23    ┆ 2001-01-01 23:00:00 │
# │ 24    ┆ 2001-01-02 00:00:00 │
# └───────┴─────────────────────┘

Compute the rolling quantile with the temporal windows closed on the right:

df_temporal.with_columns(
  rolling_row_quantile: Polars.col("index").rolling_quantile_by(
    "date", "2h", quantile: 0.3
  )
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬──────────────────────┐
# │ index ┆ date                ┆ rolling_row_quantile │
# │ ---   ┆ ---                 ┆ ---                  │
# │ u32   ┆ datetime[ns]        ┆ f64                  │
# ╞═══════╪═════════════════════╪══════════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ 0.0                  │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 0.0                  │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 1.0                  │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 2.0                  │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 3.0                  │
# │ …     ┆ …                   ┆ …                    │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 19.0                 │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 20.0                 │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 21.0                 │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 22.0                 │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 23.0                 │
# └───────┴─────────────────────┴──────────────────────┘

Parameters:

  • by (String) —

    This column must be of dtype Datetime or Date.

  • quantile (Float) —

    Quantile between 0.0 and 1.0.

  • interpolation ('nearest', 'higher', 'lower', 'midpoint', 'linear') (defaults to: "nearest") —

    Interpolation method.

  • window_size (String) —

    The length of the window. Can be a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 calendar day)
    • 1w (1 calendar week)
    • 1mo (1 calendar month)
    • 1q (1 calendar quarter)
    • 1y (1 calendar year)

    By "calendar day", we mean the corresponding time on the next day (which may not be 24 hours, due to daylight savings). Similarly for "calendar week", "calendar month", "calendar quarter", and "calendar year".

  • min_periods (Integer) (defaults to: 1) —

    The number of values in the window that should be non-null before computing a result.

  • closed ('left', 'right', 'both', 'none') (defaults to: "right") —

    Define which sides of the temporal interval are closed (inclusive), defaults to 'right'.

  • warn_if_unsorted (Boolean) (defaults to: nil) —

    Warn if data is not known to be sorted by by column.

Returns:



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# File 'lib/polars/expr.rb', line 4970

def rolling_quantile_by(
  by,
  window_size,
  quantile:,
  interpolation: "nearest",
  min_periods: 1,
  closed: "right",
  warn_if_unsorted: nil
)
  window_size = _prepare_rolling_by_window_args(window_size)
  by = Utils.parse_into_expression(by)
  _from_rbexpr(
    _rbexpr.rolling_quantile_by(
      by,
      quantile,
      interpolation,
      window_size,
      min_periods,
      closed,
    )
  )
end

#rolling_skew(window_size, bias: true) ⇒ Expr

Compute a rolling skew.

Examples:

df = Polars::DataFrame.new({"a" => [1, 4, 2, 9]})
df.select(Polars.col("a").rolling_skew(3))
# =>
# shape: (4, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ null     │
# │ null     │
# │ 0.381802 │
# │ 0.47033  │
# └──────────┘

Parameters:

  • window_size (Integer) —

    Integer size of the rolling window.

  • bias (Boolean) (defaults to: true) —

    If false, the calculations are corrected for statistical bias.

Returns:



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# File 'lib/polars/expr.rb', line 5705

def rolling_skew(window_size, bias: true)
  _from_rbexpr(_rbexpr.rolling_skew(window_size, bias))
end

#rolling_std(window_size, weights: nil, min_periods: nil, center: false, ddof: 1) ⇒ Expr

Note:

This functionality is experimental and may change without it being considered a breaking change.

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using group_by_rolling this method can cache the window size computation.

Compute a rolling standard deviation.

A window of length window_size will traverse the array. The values that fill this window will (optionally) be multiplied with the weights given by the weight vector. The resulting values will be aggregated to their sum.

Examples:

df = Polars::DataFrame.new({"A" => [1.0, 2.0, 3.0, 4.0, 6.0, 8.0]})
df.select(
  [
    Polars.col("A").rolling_std(3)
  ]
)
# =>
# shape: (6, 1)
# ┌──────────┐
# │ A        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ null     │
# │ null     │
# │ 1.0      │
# │ 1.0      │
# │ 1.527525 │
# │ 2.0      │
# └──────────┘

Parameters:

  • window_size (Integer) —

    The length of the window. Can be a fixed integer size, or a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 day)
    • 1w (1 week)
    • 1mo (1 calendar month)
    • 1y (1 calendar year)
    • 1i (1 index count)

    If a timedelta or the dynamic string language is used, the by and closed arguments must also be set.

  • weights (Array) (defaults to: nil) —

    An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.

  • min_periods (Integer) (defaults to: nil) —

    The number of values in the window that should be non-null before computing a result. If None, it will be set equal to window size.

  • center (Boolean) (defaults to: false) —

    Set the labels at the center of the window

Returns:



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# File 'lib/polars/expr.rb', line 5370

def rolling_std(
  window_size,
  weights: nil,
  min_periods: nil,
  center: false,
  ddof: 1
)
  _from_rbexpr(
    _rbexpr.rolling_std(
      window_size, weights, min_periods, center, ddof
    )
  )
end

#rolling_std_by(by, window_size, min_periods: 1, closed: "right", ddof: 1, warn_if_unsorted: nil) ⇒ Expr

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using rolling - this method can cache the window size computation.

Compute a rolling standard deviation based on another column.

Examples:

Create a DataFrame with a datetime column and a row number column

start = DateTime.new(2001, 1, 1)
stop = DateTime.new(2001, 1, 2)
df_temporal = Polars::DataFrame.new(
    {"date" => Polars.datetime_range(start, stop, "1h", eager: true)}
).with_row_index
# =>
# shape: (25, 2)
# ┌───────┬─────────────────────┐
# │ index ┆ date                │
# │ ---   ┆ ---                 │
# │ u32   ┆ datetime[ns]        │
# ╞═══════╪═════════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 │
# │ 1     ┆ 2001-01-01 01:00:00 │
# │ 2     ┆ 2001-01-01 02:00:00 │
# │ 3     ┆ 2001-01-01 03:00:00 │
# │ 4     ┆ 2001-01-01 04:00:00 │
# │ …     ┆ …                   │
# │ 20    ┆ 2001-01-01 20:00:00 │
# │ 21    ┆ 2001-01-01 21:00:00 │
# │ 22    ┆ 2001-01-01 22:00:00 │
# │ 23    ┆ 2001-01-01 23:00:00 │
# │ 24    ┆ 2001-01-02 00:00:00 │
# └───────┴─────────────────────┘

Compute the rolling std with the temporal windows closed on the right (default)

df_temporal.with_columns(
  rolling_row_std: Polars.col("index").rolling_std_by("date", "2h")
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬─────────────────┐
# │ index ┆ date                ┆ rolling_row_std │
# │ ---   ┆ ---                 ┆ ---             │
# │ u32   ┆ datetime[ns]        ┆ f64             │
# ╞═══════╪═════════════════════╪═════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ null            │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 0.707107        │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 0.707107        │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 0.707107        │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 0.707107        │
# │ …     ┆ …                   ┆ …               │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 0.707107        │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 0.707107        │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 0.707107        │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 0.707107        │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 0.707107        │
# └───────┴─────────────────────┴─────────────────┘

Compute the rolling std with the closure of windows on both sides

df_temporal.with_columns(
  rolling_row_std: Polars.col("index").rolling_std_by(
    "date", "2h", closed: "both"
  )
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬─────────────────┐
# │ index ┆ date                ┆ rolling_row_std │
# │ ---   ┆ ---                 ┆ ---             │
# │ u32   ┆ datetime[ns]        ┆ f64             │
# ╞═══════╪═════════════════════╪═════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ null            │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 0.707107        │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 1.0             │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 1.0             │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 1.0             │
# │ …     ┆ …                   ┆ …               │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 1.0             │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 1.0             │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 1.0             │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 1.0             │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 1.0             │
# └───────┴─────────────────────┴─────────────────┘

Parameters:

  • by (String) —

    This column must be of dtype Datetime or Date.

  • window_size (String) —

    The length of the window. Can be a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 calendar day)
    • 1w (1 calendar week)
    • 1mo (1 calendar month)
    • 1q (1 calendar quarter)
    • 1y (1 calendar year)

    By "calendar day", we mean the corresponding time on the next day (which may not be 24 hours, due to daylight savings). Similarly for "calendar week", "calendar month", "calendar quarter", and "calendar year".

  • min_periods (Integer) (defaults to: 1) —

    The number of values in the window that should be non-null before computing a result.

  • closed ('left', 'right', 'both', 'none') (defaults to: "right") —

    Define which sides of the temporal interval are closed (inclusive), defaults to 'right'.

  • ddof (Integer) (defaults to: 1) —

    "Delta Degrees of Freedom": The divisor for a length N window is N - ddof

  • warn_if_unsorted (Boolean) (defaults to: nil) —

    Warn if data is not known to be sorted by by column.

Returns:



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# File 'lib/polars/expr.rb', line 4611

def rolling_std_by(
  by,
  window_size,
  min_periods: 1,
  closed: "right",
  ddof: 1,
  warn_if_unsorted: nil
)
  window_size = _prepare_rolling_by_window_args(window_size)
  by = Utils.parse_into_expression(by)
  _from_rbexpr(
    _rbexpr.rolling_std_by(
      by,
      window_size,
      min_periods,
      closed,
      ddof
    )
  )
end

#rolling_sum(window_size, weights: nil, min_periods: nil, center: false) ⇒ Expr

Note:

This functionality is experimental and may change without it being considered a breaking change.

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using group_by_rolling this method can cache the window size computation.

Apply a rolling sum (moving sum) over the values in this array.

A window of length window_size will traverse the array. The values that fill this window will (optionally) be multiplied with the weights given by the weight vector. The resulting values will be aggregated to their sum.

Examples:

df = Polars::DataFrame.new({"A" => [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]})
df.select(
  [
    Polars.col("A").rolling_sum(2)
  ]
)
# =>
# shape: (6, 1)
# ┌──────┐
# │ A    │
# │ ---  │
# │ f64  │
# ╞══════╡
# │ null │
# │ 3.0  │
# │ 5.0  │
# │ 7.0  │
# │ 9.0  │
# │ 11.0 │
# └──────┘

Parameters:

  • window_size (Integer) —

    The length of the window. Can be a fixed integer size, or a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 day)
    • 1w (1 week)
    • 1mo (1 calendar month)
    • 1y (1 calendar year)
    • 1i (1 index count)

    If a timedelta or the dynamic string language is used, the by and closed arguments must also be set.

  • weights (Array) (defaults to: nil) —

    An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.

  • min_periods (Integer) (defaults to: nil) —

    The number of values in the window that should be non-null before computing a result. If None, it will be set equal to window size.

  • center (Boolean) (defaults to: false) —

    Set the labels at the center of the window

Returns:



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# File 'lib/polars/expr.rb', line 5292

def rolling_sum(
  window_size,
  weights: nil,
  min_periods: nil,
  center: false
)
  _from_rbexpr(
    _rbexpr.rolling_sum(
      window_size, weights, min_periods, center
    )
  )
end

#rolling_sum_by(by, window_size, min_periods: 1, closed: "right", warn_if_unsorted: nil) ⇒ Expr

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using rolling - this method can cache the window size computation.

Apply a rolling sum based on another column.

Examples:

Create a DataFrame with a datetime column and a row number column

start = DateTime.new(2001, 1, 1)
stop = DateTime.new(2001, 1, 2)
df_temporal = Polars::DataFrame.new(
    {"date" => Polars.datetime_range(start, stop, "1h", eager: true)}
).with_row_index
# =>
# shape: (25, 2)
# ┌───────┬─────────────────────┐
# │ index ┆ date                │
# │ ---   ┆ ---                 │
# │ u32   ┆ datetime[ns]        │
# ╞═══════╪═════════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 │
# │ 1     ┆ 2001-01-01 01:00:00 │
# │ 2     ┆ 2001-01-01 02:00:00 │
# │ 3     ┆ 2001-01-01 03:00:00 │
# │ 4     ┆ 2001-01-01 04:00:00 │
# │ …     ┆ …                   │
# │ 20    ┆ 2001-01-01 20:00:00 │
# │ 21    ┆ 2001-01-01 21:00:00 │
# │ 22    ┆ 2001-01-01 22:00:00 │
# │ 23    ┆ 2001-01-01 23:00:00 │
# │ 24    ┆ 2001-01-02 00:00:00 │
# └───────┴─────────────────────┘

Compute the rolling sum with the temporal windows closed on the right (default)

df_temporal.with_columns(
  rolling_row_sum: Polars.col("index").rolling_sum_by("date", "2h")
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬─────────────────┐
# │ index ┆ date                ┆ rolling_row_sum │
# │ ---   ┆ ---                 ┆ ---             │
# │ u32   ┆ datetime[ns]        ┆ u32             │
# ╞═══════╪═════════════════════╪═════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ 0               │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 1               │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 3               │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 5               │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 7               │
# │ …     ┆ …                   ┆ …               │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 39              │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 41              │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 43              │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 45              │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 47              │
# └───────┴─────────────────────┴─────────────────┘

Compute the rolling sum with the closure of windows on both sides

df_temporal.with_columns(
  rolling_row_sum: Polars.col("index").rolling_sum_by(
    "date", "2h", closed: "both"
  )
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬─────────────────┐
# │ index ┆ date                ┆ rolling_row_sum │
# │ ---   ┆ ---                 ┆ ---             │
# │ u32   ┆ datetime[ns]        ┆ u32             │
# ╞═══════╪═════════════════════╪═════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ 0               │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 1               │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 3               │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 6               │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 9               │
# │ …     ┆ …                   ┆ …               │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 57              │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 60              │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 63              │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 66              │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 69              │
# └───────┴─────────────────────┴─────────────────┘

Parameters:

  • by (String) —

    This column must of dtype {Date, Datetime}

  • window_size (String) —

    The length of the window. Can be a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 calendar day)
    • 1w (1 calendar week)
    • 1mo (1 calendar month)
    • 1q (1 calendar quarter)
    • 1y (1 calendar year)

    By "calendar day", we mean the corresponding time on the next day (which may not be 24 hours, due to daylight savings). Similarly for "calendar week", "calendar month", "calendar quarter", and "calendar year".

  • min_periods (Integer) (defaults to: 1) —

    The number of values in the window that should be non-null before computing a result.

  • closed ('left', 'right', 'both', 'none') (defaults to: "right") —

    Define which sides of the temporal interval are closed (inclusive), defaults to 'right'.

  • warn_if_unsorted (Boolean) (defaults to: nil) —

    Warn if data is not known to be sorted by by column.

Returns:



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# File 'lib/polars/expr.rb', line 4480

def rolling_sum_by(
  by,
  window_size,
  min_periods: 1,
  closed: "right",
  warn_if_unsorted: nil
)
  window_size = _prepare_rolling_by_window_args(window_size)
  by = Utils.parse_into_expression(by)
  _from_rbexpr(
    _rbexpr.rolling_sum_by(by, window_size, min_periods, closed)
  )
end

#rolling_var(window_size, weights: nil, min_periods: nil, center: false, ddof: 1) ⇒ Expr

Note:

This functionality is experimental and may change without it being considered a breaking change.

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using group_by_rolling this method can cache the window size computation.

Compute a rolling variance.

A window of length window_size will traverse the array. The values that fill this window will (optionally) be multiplied with the weights given by the weight vector. The resulting values will be aggregated to their sum.

Examples:

df = Polars::DataFrame.new({"A" => [1.0, 2.0, 3.0, 4.0, 6.0, 8.0]})
df.select(
  [
    Polars.col("A").rolling_var(3)
  ]
)
# =>
# shape: (6, 1)
# ┌──────────┐
# │ A        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ null     │
# │ null     │
# │ 1.0      │
# │ 1.0      │
# │ 2.333333 │
# │ 4.0      │
# └──────────┘

Parameters:

  • window_size (Integer) —

    The length of the window. Can be a fixed integer size, or a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 day)
    • 1w (1 week)
    • 1mo (1 calendar month)
    • 1y (1 calendar year)
    • 1i (1 index count)

    If a timedelta or the dynamic string language is used, the by and closed arguments must also be set.

  • weights (Array) (defaults to: nil) —

    An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.

  • min_periods (Integer) (defaults to: nil) —

    The number of values in the window that should be non-null before computing a result. If None, it will be set equal to window size.

  • center (Boolean) (defaults to: false) —

    Set the labels at the center of the window

Returns:



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# File 'lib/polars/expr.rb', line 5449

def rolling_var(
  window_size,
  weights: nil,
  min_periods: nil,
  center: false,
  ddof: 1
)
  _from_rbexpr(
    _rbexpr.rolling_var(
      window_size, weights, min_periods, center, ddof
    )
  )
end

#rolling_var_by(by, window_size, min_periods: 1, closed: "right", ddof: 1, warn_if_unsorted: nil) ⇒ Expr

Note:

If you want to compute multiple aggregation statistics over the same dynamic window, consider using rolling - this method can cache the window size computation.

Compute a rolling variance based on another column.

Examples:

Create a DataFrame with a datetime column and a row number column

start = DateTime.new(2001, 1, 1)
stop = DateTime.new(2001, 1, 2)
df_temporal = Polars::DataFrame.new(
    {"date" => Polars.datetime_range(start, stop, "1h", eager: true)}
).with_row_index
# =>
# shape: (25, 2)
# ┌───────┬─────────────────────┐
# │ index ┆ date                │
# │ ---   ┆ ---                 │
# │ u32   ┆ datetime[ns]        │
# ╞═══════╪═════════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 │
# │ 1     ┆ 2001-01-01 01:00:00 │
# │ 2     ┆ 2001-01-01 02:00:00 │
# │ 3     ┆ 2001-01-01 03:00:00 │
# │ 4     ┆ 2001-01-01 04:00:00 │
# │ …     ┆ …                   │
# │ 20    ┆ 2001-01-01 20:00:00 │
# │ 21    ┆ 2001-01-01 21:00:00 │
# │ 22    ┆ 2001-01-01 22:00:00 │
# │ 23    ┆ 2001-01-01 23:00:00 │
# │ 24    ┆ 2001-01-02 00:00:00 │
# └───────┴─────────────────────┘

Compute the rolling var with the temporal windows closed on the right (default)

df_temporal.with_columns(
  rolling_row_var: Polars.col("index").rolling_var_by("date", "2h")
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬─────────────────┐
# │ index ┆ date                ┆ rolling_row_var │
# │ ---   ┆ ---                 ┆ ---             │
# │ u32   ┆ datetime[ns]        ┆ f64             │
# ╞═══════╪═════════════════════╪═════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ null            │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 0.5             │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 0.5             │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 0.5             │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 0.5             │
# │ …     ┆ …                   ┆ …               │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 0.5             │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 0.5             │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 0.5             │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 0.5             │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 0.5             │
# └───────┴─────────────────────┴─────────────────┘

Compute the rolling var with the closure of windows on both sides

df_temporal.with_columns(
  rolling_row_var: Polars.col("index").rolling_var_by(
    "date", "2h", closed: "both"
  )
)
# =>
# shape: (25, 3)
# ┌───────┬─────────────────────┬─────────────────┐
# │ index ┆ date                ┆ rolling_row_var │
# │ ---   ┆ ---                 ┆ ---             │
# │ u32   ┆ datetime[ns]        ┆ f64             │
# ╞═══════╪═════════════════════╪═════════════════╡
# │ 0     ┆ 2001-01-01 00:00:00 ┆ null            │
# │ 1     ┆ 2001-01-01 01:00:00 ┆ 0.5             │
# │ 2     ┆ 2001-01-01 02:00:00 ┆ 1.0             │
# │ 3     ┆ 2001-01-01 03:00:00 ┆ 1.0             │
# │ 4     ┆ 2001-01-01 04:00:00 ┆ 1.0             │
# │ …     ┆ …                   ┆ …               │
# │ 20    ┆ 2001-01-01 20:00:00 ┆ 1.0             │
# │ 21    ┆ 2001-01-01 21:00:00 ┆ 1.0             │
# │ 22    ┆ 2001-01-01 22:00:00 ┆ 1.0             │
# │ 23    ┆ 2001-01-01 23:00:00 ┆ 1.0             │
# │ 24    ┆ 2001-01-02 00:00:00 ┆ 1.0             │
# └───────┴─────────────────────┴─────────────────┘

Parameters:

  • by (String) —

    This column must be of dtype Datetime or Date.

  • window_size (String) —

    The length of the window. Can be a dynamic temporal size indicated by a timedelta or the following string language:

    • 1ns (1 nanosecond)
    • 1us (1 microsecond)
    • 1ms (1 millisecond)
    • 1s (1 second)
    • 1m (1 minute)
    • 1h (1 hour)
    • 1d (1 calendar day)
    • 1w (1 calendar week)
    • 1mo (1 calendar month)
    • 1q (1 calendar quarter)
    • 1y (1 calendar year)

    By "calendar day", we mean the corresponding time on the next day (which may not be 24 hours, due to daylight savings). Similarly for "calendar week", "calendar month", "calendar quarter", and "calendar year".

  • min_periods (Integer) (defaults to: 1) —

    The number of values in the window that should be non-null before computing a result.

  • closed ('left', 'right', 'both', 'none') (defaults to: "right") —

    Define which sides of the temporal interval are closed (inclusive), defaults to 'right'.

  • ddof (Integer) (defaults to: 1) —

    "Delta Degrees of Freedom": The divisor for a length N window is N - ddof

  • warn_if_unsorted (Boolean) (defaults to: nil) —

    Warn if data is not known to be sorted by by column.

Returns:



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# File 'lib/polars/expr.rb', line 4749

def rolling_var_by(
  by,
  window_size,
  min_periods: 1,
  closed: "right",
  ddof: 1,
  warn_if_unsorted: nil
)
  window_size = _prepare_rolling_by_window_args(window_size)
  by = Utils.parse_into_expression(by)
  _from_rbexpr(
    _rbexpr.rolling_var_by(
      by,
      window_size,
      min_periods,
      closed,
      ddof
    )
  )
end

#round(decimals = 0) ⇒ Expr

Round underlying floating point data by decimals digits.

Examples:

df = Polars::DataFrame.new({"a" => [0.33, 0.52, 1.02, 1.17]})
df.select(Polars.col("a").round(1))
# =>
# shape: (4, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 0.3 │
# │ 0.5 │
# │ 1.0 │
# │ 1.2 │
# └─────┘

Parameters:

  • decimals (Integer) (defaults to: 0) —

    Number of decimals to round by.

Returns:



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# File 'lib/polars/expr.rb', line 1179

def round(decimals = 0)
  _from_rbexpr(_rbexpr.round(decimals))
end

#sample(frac: nil, with_replacement: true, shuffle: false, seed: nil, n: nil) ⇒ Expr

Sample from this expression.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3]})
df.select(Polars.col("a").sample(frac: 1.0, with_replacement: true, seed: 1))
# =>
# shape: (3, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 3   │
# │ 1   │
# │ 1   │
# └─────┘

Parameters:

  • frac (Float) (defaults to: nil) —

    Fraction of items to return. Cannot be used with n.

  • with_replacement (Boolean) (defaults to: true) —

    Allow values to be sampled more than once.

  • shuffle (Boolean) (defaults to: false) —

    Shuffle the order of sampled data points.

  • seed (Integer) (defaults to: nil) —

    Seed for the random number generator. If set to None (default), a random seed is used.

  • n (Integer) (defaults to: nil) —

    Number of items to return. Cannot be used with frac.

Returns:



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# File 'lib/polars/expr.rb', line 6476

def sample(
  frac: nil,
  with_replacement: true,
  shuffle: false,
  seed: nil,
  n: nil
)
  if !n.nil? && !frac.nil?
    raise ArgumentError, "cannot specify both `n` and `frac`"
  end

  if !n.nil? && frac.nil?
    n = Utils.parse_into_expression(n)
    return _from_rbexpr(_rbexpr.sample_n(n, with_replacement, shuffle, seed))
  end

  if frac.nil?
    frac = 1.0
  end
  frac = Utils.parse_into_expression(frac)
  _from_rbexpr(
    _rbexpr.sample_frac(frac, with_replacement, shuffle, seed)
  )
end

#search_sorted(element, side: "any") ⇒ Expr

Find indices where elements should be inserted to maintain order.

Examples:

df = Polars::DataFrame.new(
  {
    "values" => [1, 2, 3, 5]
  }
)
df.select(
  [
    Polars.col("values").search_sorted(0).alias("zero"),
    Polars.col("values").search_sorted(3).alias("three"),
    Polars.col("values").search_sorted(6).alias("six")
  ]
)
# =>
# shape: (1, 3)
# ┌──────┬───────┬─────┐
# │ zero ┆ three ┆ six │
# │ ---  ┆ ---   ┆ --- │
# │ u32  ┆ u32   ┆ u32 │
# ╞══════╪═══════╪═════╡
# │ 0    ┆ 2     ┆ 4   │
# └──────┴───────┴─────┘

Parameters:

  • element (Object) —

    Expression or scalar value.

Returns:



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# File 'lib/polars/expr.rb', line 1540

def search_sorted(element, side: "any")
  element = Utils.parse_into_expression(element, str_as_lit: false)
  _from_rbexpr(_rbexpr.search_sorted(element, side))
end

#set_sorted(descending: false) ⇒ Expr

Note:

This can lead to incorrect results if this Series is not sorted!! Use with care!

Flags the expression as 'sorted'.

Enables downstream code to user fast paths for sorted arrays.

Examples:

df = Polars::DataFrame.new({"values" => [1, 2, 3]})
df.select(Polars.col("values").set_sorted.max)
# =>
# shape: (1, 1)
# ┌────────┐
# │ values │
# │ ---    │
# │ i64    │
# ╞════════╡
# │ 3      │
# └────────┘

Parameters:

  • descending (Boolean) (defaults to: false) —

    Whether the Series order is descending.

Returns:



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# File 'lib/polars/expr.rb', line 6853

def set_sorted(descending: false)
  _from_rbexpr(_rbexpr.set_sorted_flag(descending))
end

#shift(n = 1, fill_value: nil) ⇒ Expr

Shift the values by a given period.

Examples:

df = Polars::DataFrame.new({"foo" => [1, 2, 3, 4]})
df.select(Polars.col("foo").shift(1))
# =>
# shape: (4, 1)
# ┌──────┐
# │ foo  │
# │ ---  │
# │ i64  │
# ╞══════╡
# │ null │
# │ 1    │
# │ 2    │
# │ 3    │
# └──────┘

Parameters:

  • n (Integer) (defaults to: 1) —

    Number of places to shift (may be negative).

  • fill_value (Object) (defaults to: nil) —

    Fill the resulting null values with this value.

Returns:



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# File 'lib/polars/expr.rb', line 1701

def shift(n = 1, fill_value: nil)
  if !fill_value.nil?
    fill_value = Utils.parse_into_expression(fill_value, str_as_lit: true)
  end
  n = Utils.parse_into_expression(n)
  _from_rbexpr(_rbexpr.shift(n, fill_value))
end

#shift_and_fill(periods, fill_value) ⇒ Expr

Shift the values by a given period and fill the resulting null values.

Examples:

df = Polars::DataFrame.new({"foo" => [1, 2, 3, 4]})
df.select(Polars.col("foo").shift_and_fill(1, "a"))
# =>
# shape: (4, 1)
# ┌─────┐
# │ foo │
# │ --- │
# │ str │
# ╞═════╡
# │ a   │
# │ 1   │
# │ 2   │
# │ 3   │
# └─────┘

Parameters:

  • periods (Integer) —

    Number of places to shift (may be negative).

  • fill_value (Object) —

    Fill nil values with the result of this expression.

Returns:



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# File 'lib/polars/expr.rb', line 1733

def shift_and_fill(periods, fill_value)
  shift(periods, fill_value: fill_value)
end

#shrink_dtype ⇒ Expr

Shrink numeric columns to the minimal required datatype.

Shrink to the dtype needed to fit the extrema of this Series. This can be used to reduce memory pressure.

Examples:

Polars::DataFrame.new(
  {
    "a" => [1, 2, 3],
    "b" => [1, 2, 2 << 32],
    "c" => [-1, 2, 1 << 30],
    "d" => [-112, 2, 112],
    "e" => [-112, 2, 129],
    "f" => ["a", "b", "c"],
    "g" => [0.1, 1.32, 0.12],
    "h" => [true, nil, false]
  }
).select(Polars.all.shrink_dtype)
# =>
# shape: (3, 8)
# ┌─────┬────────────┬────────────┬──────┬──────┬─────┬──────┬───────┐
# │ a   ┆ b          ┆ c          ┆ d    ┆ e    ┆ f   ┆ g    ┆ h     │
# │ --- ┆ ---        ┆ ---        ┆ ---  ┆ ---  ┆ --- ┆ ---  ┆ ---   │
# │ i8  ┆ i64        ┆ i32        ┆ i8   ┆ i16  ┆ str ┆ f32  ┆ bool  │
# ╞═════╪════════════╪════════════╪══════╪══════╪═════╪══════╪═══════╡
# │ 1   ┆ 1          ┆ -1         ┆ -112 ┆ -112 ┆ a   ┆ 0.1  ┆ true  │
# │ 2   ┆ 2          ┆ 2          ┆ 2    ┆ 2    ┆ b   ┆ 1.32 ┆ null  │
# │ 3   ┆ 8589934592 ┆ 1073741824 ┆ 112  ┆ 129  ┆ c   ┆ 0.12 ┆ false │
# └─────┴────────────┴────────────┴──────┴──────┴─────┴──────┴───────┘

Returns:



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# File 'lib/polars/expr.rb', line 6913

def shrink_dtype
  _from_rbexpr(_rbexpr.shrink_dtype)
end

#shuffle(seed: nil) ⇒ Expr

Shuffle the contents of this expr.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3]})
df.select(Polars.col("a").shuffle(seed: 1))
# =>
# shape: (3, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 2   │
# │ 1   │
# │ 3   │
# └─────┘

Parameters:

  • seed (Integer) (defaults to: nil) —

    Seed for the random number generator. If set to None (default), a random seed is generated using the random module.

Returns:



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# File 'lib/polars/expr.rb', line 6439

def shuffle(seed: nil)
  if seed.nil?
    seed = rand(10000)
  end
  _from_rbexpr(_rbexpr.shuffle(seed))
end

#sign ⇒ Expr

Compute the element-wise indication of the sign.

Examples:

df = Polars::DataFrame.new({"a" => [-9.0, -0.0, 0.0, 4.0, nil]})
df.select(Polars.col("a").sign)
# =>
# shape: (5, 1)
# ┌──────┐
# │ a    │
# │ ---  │
# │ f64  │
# ╞══════╡
# │ -1.0 │
# │ -0.0 │
# │ 0.0  │
# │ 1.0  │
# │ null │
# └──────┘

Returns:



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# File 'lib/polars/expr.rb', line 6127

def sign
  _from_rbexpr(_rbexpr.sign)
end

#sin ⇒ Expr

Compute the element-wise value for the sine.

Examples:

df = Polars::DataFrame.new({"a" => [0.0]})
df.select(Polars.col("a").sin)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 0.0 │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 6147

def sin
  _from_rbexpr(_rbexpr.sin)
end

#sinh ⇒ Expr

Compute the element-wise value for the hyperbolic sine.

Examples:

df = Polars::DataFrame.new({"a" => [1.0]})
df.select(Polars.col("a").sinh)
# =>
# shape: (1, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 1.175201 │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6267

def sinh
  _from_rbexpr(_rbexpr.sinh)
end

#skew(bias: true) ⇒ Expr

Compute the sample skewness of a data set.

For normally distributed data, the skewness should be about zero. For unimodal continuous distributions, a skewness value greater than zero means that there is more weight in the right tail of the distribution. The function skewtest can be used to determine if the skewness value is close enough to zero, statistically speaking.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3, 2, 1]})
df.select(Polars.col("a").skew)
# =>
# shape: (1, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 0.343622 │
# └──────────┘

Parameters:

  • bias (Boolean) (defaults to: true) —

    If false, the calculations are corrected for statistical bias.

Returns:



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# File 'lib/polars/expr.rb', line 5926

def skew(bias: true)
  _from_rbexpr(_rbexpr.skew(bias))
end

#slice(offset, length = nil) ⇒ Expr

Get a slice of this expression.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [8, 9, 10, 11],
    "b" => [nil, 4, 4, 4]
  }
)
df.select(Polars.all.slice(1, 2))
# =>
# shape: (2, 2)
# ┌─────┬─────┐
# │ a   ┆ b   │
# │ --- ┆ --- │
# │ i64 ┆ i64 │
# ╞═════╪═════╡
# │ 9   ┆ 4   │
# │ 10  ┆ 4   │
# └─────┴─────┘

Parameters:

  • offset (Integer) —

    Start index. Negative indexing is supported.

  • length (Integer) (defaults to: nil) —

    Length of the slice. If set to nil, all rows starting at the offset will be selected.

Returns:



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# File 'lib/polars/expr.rb', line 814

def slice(offset, length = nil)
  if !offset.is_a?(Expr)
    offset = Polars.lit(offset)
  end
  if !length.is_a?(Expr)
    length = Polars.lit(length)
  end
  _from_rbexpr(_rbexpr.slice(offset._rbexpr, length._rbexpr))
end

#sort(reverse: false, nulls_last: false) ⇒ Expr

Sort this column. In projection/ selection context the whole column is sorted.

If used in a group by context, the groups are sorted.

Examples:

df = Polars::DataFrame.new(
  {
    "group" => [
      "one",
      "one",
      "one",
      "two",
      "two",
      "two"
    ],
    "value" => [1, 98, 2, 3, 99, 4]
  }
)
df.select(Polars.col("value").sort)
# =>
# shape: (6, 1)
# ┌───────┐
# │ value │
# │ ---   │
# │ i64   │
# ╞═══════╡
# │ 1     │
# │ 2     │
# │ 3     │
# │ 4     │
# │ 98    │
# │ 99    │
# └───────┘
df.select(Polars.col("value").sort)
# =>
# shape: (6, 1)
# ┌───────┐
# │ value │
# │ ---   │
# │ i64   │
# ╞═══════╡
# │ 1     │
# │ 2     │
# │ 3     │
# │ 4     │
# │ 98    │
# │ 99    │
# └───────┘
df.group_by("group").agg(Polars.col("value").sort)
# =>
# shape: (2, 2)
# ┌───────┬────────────┐
# │ group ┆ value      │
# │ ---   ┆ ---        │
# │ str   ┆ list[i64]  │
# ╞═══════╪════════════╡
# │ two   ┆ [3, 4, 99] │
# │ one   ┆ [1, 2, 98] │
# └───────┴────────────┘

Parameters:

  • reverse (Boolean) (defaults to: false) —

    false -> order from small to large. true -> order from large to small.

  • nulls_last (Boolean) (defaults to: false) —

    If true nulls are considered to be larger than any valid value.

Returns:



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# File 'lib/polars/expr.rb', line 1350

def sort(reverse: false, nulls_last: false)
  _from_rbexpr(_rbexpr.sort_with(reverse, nulls_last))
end

#sort_by(by, *more_by, reverse: false, nulls_last: false, multithreaded: true, maintain_order: false) ⇒ Expr

Sort this column by the ordering of another column, or multiple other columns.

In projection/ selection context the whole column is sorted. If used in a group by context, the groups are sorted.

Examples:

df = Polars::DataFrame.new(
  {
    "group" => [
      "one",
      "one",
      "one",
      "two",
      "two",
      "two"
    ],
    "value" => [1, 98, 2, 3, 99, 4]
  }
)
df.select(Polars.col("group").sort_by("value"))
# =>
# shape: (6, 1)
# ┌───────┐
# │ group │
# │ ---   │
# │ str   │
# ╞═══════╡
# │ one   │
# │ one   │
# │ two   │
# │ two   │
# │ one   │
# │ two   │
# └───────┘

Parameters:

  • by (Object) —

    The column(s) used for sorting.

  • reverse (Boolean) (defaults to: false) —

    false -> order from small to large. true -> order from large to small.

Returns:



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# File 'lib/polars/expr.rb', line 1587

def sort_by(by, *more_by, reverse: false, nulls_last: false, multithreaded: true, maintain_order: false)
  by = Utils.parse_into_list_of_expressions(by, *more_by)
  reverse = Utils.extend_bool(reverse, by.length, "reverse", "by")
  nulls_last = Utils.extend_bool(nulls_last, by.length, "nulls_last", "by")
  _from_rbexpr(
    _rbexpr.sort_by(
      by, reverse, nulls_last, multithreaded, maintain_order
    )
  )
end

#sqrt ⇒ Expr

Compute the square root of the elements.

Examples:

df = Polars::DataFrame.new({"values" => [1.0, 2.0, 4.0]})
df.select(Polars.col("values").sqrt)
# =>
# shape: (3, 1)
# ┌──────────┐
# │ values   │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 1.0      │
# │ 1.414214 │
# │ 2.0      │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 245

def sqrt
  self**0.5
end

#std(ddof: 1) ⇒ Expr

Get standard deviation.

Examples:

df = Polars::DataFrame.new({"a" => [-1, 0, 1]})
df.select(Polars.col("a").std)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 1.0 │
# └─────┘

Parameters:

  • ddof (Integer) (defaults to: 1) —

    Degrees of freedom.

Returns:



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# File 'lib/polars/expr.rb', line 1958

def std(ddof: 1)
  _from_rbexpr(_rbexpr.std(ddof))
end

#str ⇒ StringExpr

Create an object namespace of all string related methods.

Returns:



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# File 'lib/polars/expr.rb', line 7282

def str
  StringExpr.new(self)
end

#struct ⇒ StructExpr

Create an object namespace of all struct related methods.

Returns:



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# File 'lib/polars/expr.rb', line 7289

def struct
  StructExpr.new(self)
end

#sub(other) ⇒ Expr

Method equivalent of subtraction operator expr - other.

Examples:

df = Polars::DataFrame.new({"x" => [0, 1, 2, 3, 4]})
df.with_columns(
  Polars.col("x").sub(2).alias("x-2"),
  Polars.col("x").sub(Polars.col("x").cum_sum).alias("x-expr"),
)
# =>
# shape: (5, 3)
# ┌─────┬─────┬────────┐
# │ x   ┆ x-2 ┆ x-expr │
# │ --- ┆ --- ┆ ---    │
# │ i64 ┆ i64 ┆ i64    │
# ╞═════╪═════╪════════╡
# │ 0   ┆ -2  ┆ 0      │
# │ 1   ┆ -1  ┆ 0      │
# │ 2   ┆ 0   ┆ -1     │
# │ 3   ┆ 1   ┆ -3     │
# │ 4   ┆ 2   ┆ -6     │
# └─────┴─────┴────────┘

Parameters:

  • other (Object) —

    Numeric literal or expression value.

Returns:



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# File 'lib/polars/expr.rb', line 3598

def sub(other)
  self - other
end

#suffix(suffix) ⇒ Expr

Add a suffix to the root column name of the expression.

Examples:

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, 3],
    "b" => ["x", "y", "z"]
  }
)
df.with_columns(Polars.all.reverse.name.suffix("_reverse"))
# =>
# shape: (3, 4)
# ┌─────┬─────┬───────────┬───────────┐
# │ a   ┆ b   ┆ a_reverse ┆ b_reverse │
# │ --- ┆ --- ┆ ---       ┆ ---       │
# │ i64 ┆ str ┆ i64       ┆ str       │
# ╞═════╪═════╪═══════════╪═══════════╡
# │ 1   ┆ x   ┆ 3         ┆ z         │
# │ 2   ┆ y   ┆ 2         ┆ y         │
# │ 3   ┆ z   ┆ 1         ┆ x         │
# └─────┴─────┴───────────┴───────────┘

Returns:



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# File 'lib/polars/expr.rb', line 461

def suffix(suffix)
  name.suffix(suffix)
end

#sum ⇒ Expr

Note:

Dtypes in :i8, :u8, :i16, and :u16 are cast to :i64 before summing to prevent overflow issues.

Get sum value.

Examples:

df = Polars::DataFrame.new({"a" => [-1, 0, 1]})
df.select(Polars.col("a").sum)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 0   │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 2085

def sum
  _from_rbexpr(_rbexpr.sum)
end

#tail(n = 10) ⇒ Expr

Get the last n rows.

Examples:

df = Polars::DataFrame.new({"foo" => [1, 2, 3, 4, 5, 6, 7]})
df.tail(3)
# =>
# shape: (3, 1)
# ┌─────┐
# │ foo │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 5   │
# │ 6   │
# │ 7   │
# └─────┘

Parameters:

  • n (Integer) (defaults to: 10) —

    Number of rows to return.

Returns:



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# File 'lib/polars/expr.rb', line 3132

def tail(n = 10)
  _from_rbexpr(_rbexpr.tail(n))
end

#tan ⇒ Expr

Compute the element-wise value for the tangent.

Examples:

df = Polars::DataFrame.new({"a" => [1.0]})
df.select(Polars.col("a").tan)
# =>
# shape: (1, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 1.557408 │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6187

def tan
  _from_rbexpr(_rbexpr.tan)
end

#tanh ⇒ Expr

Compute the element-wise value for the hyperbolic tangent.

Examples:

df = Polars::DataFrame.new({"a" => [1.0]})
df.select(Polars.col("a").tanh)
# =>
# shape: (1, 1)
# ┌──────────┐
# │ a        │
# │ ---      │
# │ f64      │
# ╞══════════╡
# │ 0.761594 │
# └──────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6307

def tanh
  _from_rbexpr(_rbexpr.tanh)
end

#to_physical ⇒ Expr

Cast to physical representation of the logical dtype.

  • :date -> :i32
  • :datetime -> :i64
  • :time -> :i64
  • :duration -> :i64
  • :cat -> :u32
  • Other data types will be left unchanged.

Examples:

Polars::DataFrame.new({"vals" => ["a", "x", nil, "a"]}).with_columns(
  [
    Polars.col("vals").cast(:cat),
    Polars.col("vals")
      .cast(:cat)
      .to_physical
      .alias("vals_physical")
  ]
)
# =>
# shape: (4, 2)
# ┌──────┬───────────────┐
# │ vals ┆ vals_physical │
# │ ---  ┆ ---           │
# │ cat  ┆ u32           │
# ╞══════╪═══════════════╡
# │ a    ┆ 0             │
# │ x    ┆ 1             │
# │ null ┆ null          │
# │ a    ┆ 0             │
# └──────┴───────────────┘

Returns:



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# File 'lib/polars/expr.rb', line 178

def to_physical
  _from_rbexpr(_rbexpr.to_physical)
end

#to_s ⇒ String Also known as: inspect

Returns a string representing the Expr.

Returns:



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# File 'lib/polars/expr.rb', line 20

def to_s
  _rbexpr.to_str
end

#top_k(k: 5) ⇒ Expr

Return the k largest elements.

If 'reverse: true` the smallest elements will be given.

Examples:

df = Polars::DataFrame.new(
  {
    "value" => [1, 98, 2, 3, 99, 4]
  }
)
df.select(
  [
    Polars.col("value").top_k.alias("top_k"),
    Polars.col("value").bottom_k.alias("bottom_k")
  ]
)
# =>
# shape: (5, 2)
# ┌───────┬──────────┐
# │ top_k ┆ bottom_k │
# │ ---   ┆ ---      │
# │ i64   ┆ i64      │
# ╞═══════╪══════════╡
# │ 99    ┆ 1        │
# │ 98    ┆ 2        │
# │ 4     ┆ 3        │
# │ 3     ┆ 4        │
# │ 2     ┆ 98       │
# └───────┴──────────┘

Parameters:

  • k (Integer) (defaults to: 5) —

    Number of elements to return.

Returns:



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# File 'lib/polars/expr.rb', line 1388

def top_k(k: 5)
  k = Utils.parse_into_expression(k)
  _from_rbexpr(_rbexpr.top_k(k))
end

#truediv(other) ⇒ Expr

Method equivalent of float division operator expr / other.

Examples:

df = Polars::DataFrame.new(
  {"x" => [-2, -1, 0, 1, 2], "y" => [0.5, 0.0, 0.0, -4.0, -0.5]}
)
df.with_columns(
  Polars.col("x").truediv(2).alias("x/2"),
  Polars.col("x").truediv(Polars.col("y")).alias("x/y")
)
# =>
# shape: (5, 4)
# ┌─────┬──────┬──────┬───────┐
# │ x   ┆ y    ┆ x/2  ┆ x/y   │
# │ --- ┆ ---  ┆ ---  ┆ ---   │
# │ i64 ┆ f64  ┆ f64  ┆ f64   │
# ╞═════╪══════╪══════╪═══════╡
# │ -2  ┆ 0.5  ┆ -1.0 ┆ -4.0  │
# │ -1  ┆ 0.0  ┆ -0.5 ┆ -inf  │
# │ 0   ┆ 0.0  ┆ 0.0  ┆ NaN   │
# │ 1   ┆ -4.0 ┆ 0.5  ┆ -0.25 │
# │ 2   ┆ -0.5 ┆ 1.0  ┆ -4.0  │
# └─────┴──────┴──────┴───────┘

Parameters:

  • other (Object) —

    Numeric literal or expression value.

Returns:



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# File 'lib/polars/expr.rb', line 3653

def truediv(other)
  self / other
end

#unique(maintain_order: false) ⇒ Expr

Get unique values of this expression.

Examples:

df = Polars::DataFrame.new({"a" => [1, 1, 2]})
df.select(Polars.col("a").unique(maintain_order: true))
# =>
# shape: (2, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ i64 │
# ╞═════╡
# │ 1   │
# │ 2   │
# └─────┘

Parameters:

  • maintain_order (Boolean) (defaults to: false) —

    Maintain order of data. This requires more work.

Returns:



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# File 'lib/polars/expr.rb', line 2277

def unique(maintain_order: false)
  if maintain_order
    _from_rbexpr(_rbexpr.unique_stable)
  else
    _from_rbexpr(_rbexpr.unique)
  end
end

#unique_counts ⇒ Expr

Return a count of the unique values in the order of appearance.

This method differs from value_counts in that it does not return the values, only the counts and might be faster

Examples:

df = Polars::DataFrame.new(
  {
    "id" => ["a", "b", "b", "c", "c", "c"]
  }
)
df.select(
  [
    Polars.col("id").unique_counts
  ]
)
# =>
# shape: (3, 1)
# ┌─────┐
# │ id  │
# │ --- │
# │ u32 │
# ╞═════╡
# │ 1   │
# │ 2   │
# │ 3   │
# └─────┘

Returns:



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# File 'lib/polars/expr.rb', line 6711

def unique_counts
  _from_rbexpr(_rbexpr.unique_counts)
end

#upper_bound ⇒ Expr

Calculate the upper bound.

Returns a unit Series with the highest value possible for the dtype of this expression.

Examples:

df = Polars::DataFrame.new({"a" => [1, 2, 3, 2, 1]})
df.select(Polars.col("a").upper_bound)
# =>
# shape: (1, 1)
# ┌─────────────────────┐
# │ a                   │
# │ ---                 │
# │ i64                 │
# ╞═════════════════════╡
# │ 9223372036854775807 │
# └─────────────────────┘

Returns:



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# File 'lib/polars/expr.rb', line 6103

def upper_bound
  _from_rbexpr(_rbexpr.upper_bound)
end

#value_counts(sort: false, parallel: false, name: nil, normalize: false) ⇒ Expr

Count all unique values and create a struct mapping value to count.

Examples:

df = Polars::DataFrame.new(
  {
    "id" => ["a", "b", "b", "c", "c", "c"]
  }
)
df.select(
  [
    Polars.col("id").value_counts(sort: true),
  ]
)
# =>
# shape: (3, 1)
# ┌───────────┐
# │ id        │
# │ ---       │
# │ struct[2] │
# ╞═══════════╡
# │ {"c",3}   │
# │ {"b",2}   │
# │ {"a",1}   │
# └───────────┘

Parameters:

  • sort (Boolean) (defaults to: false) —

    Sort the output by count in descending order. If set to false (default), the order of the output is random.

  • parallel (Boolean) (defaults to: false) —

    Execute the computation in parallel.

  • name (String) (defaults to: nil) —

    Give the resulting count column a specific name; if normalize is true defaults to "count", otherwise defaults to "proportion".

  • normalize (Boolean) (defaults to: false) —

    If true gives relative frequencies of the unique values

Returns:



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# File 'lib/polars/expr.rb', line 6664

def value_counts(
  sort: false,
  parallel: false,
  name: nil,
  normalize: false
)
  if name.nil?
    if normalize
      name = "proportion"
    else
      name = "count"
    end
  end
  _from_rbexpr(
    _rbexpr.value_counts(sort, parallel, name, normalize)
  )
end

#var(ddof: 1) ⇒ Expr

Get variance.

Examples:

df = Polars::DataFrame.new({"a" => [-1, 0, 1]})
df.select(Polars.col("a").var)
# =>
# shape: (1, 1)
# ┌─────┐
# │ a   │
# │ --- │
# │ f64 │
# ╞═════╡
# │ 1.0 │
# └─────┘

Parameters:

  • ddof (Integer) (defaults to: 1) —

    Degrees of freedom.

Returns:



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# File 'lib/polars/expr.rb', line 1981

def var(ddof: 1)
  _from_rbexpr(_rbexpr.var(ddof))
end

#where(predicate) ⇒ Expr

Filter a single column.

Alias for #filter.

Examples:

df = Polars::DataFrame.new(
  {
    "group_col" => ["g1", "g1", "g2"],
    "b" => [1, 2, 3]
  }
)
(
  df.group_by("group_col").agg(
    [
      Polars.col("b").where(Polars.col("b") < 2).sum.alias("lt"),
      Polars.col("b").where(Polars.col("b") >= 2).sum.alias("gte")
    ]
  )
).sort("group_col")
# =>
# shape: (2, 3)
# ┌───────────┬─────┬─────┐
# │ group_col ┆ lt  ┆ gte │
# │ ---       ┆ --- ┆ --- │
# │ str       ┆ i64 ┆ i64 │
# ╞═══════════╪═════╪═════╡
# │ g1        ┆ 1   ┆ 2   │
# │ g2        ┆ 0   ┆ 3   │
# └───────────┴─────┴─────┘

Parameters:

  • predicate (Expr) —

    Boolean expression.

Returns:



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# File 'lib/polars/expr.rb', line 2857

def where(predicate)
  filter(predicate)
end

#xor(other) ⇒ Expr

Method equivalent of bitwise exclusive-or operator expr ^ other.

Examples:

df = Polars::DataFrame.new(
  {"x" => [true, false, true, false], "y" => [true, true, false, false]}
)
df.with_columns(Polars.col("x").xor(Polars.col("y")).alias("x ^ y"))
# =>
# shape: (4, 3)
# ┌───────┬───────┬───────┐
# │ x     ┆ y     ┆ x ^ y │
# │ ---   ┆ ---   ┆ ---   │
# │ bool  ┆ bool  ┆ bool  │
# ╞═══════╪═══════╪═══════╡
# │ true  ┆ true  ┆ false │
# │ false ┆ true  ┆ true  │
# │ true  ┆ false ┆ true  │
# │ false ┆ false ┆ false │
# └───────┴───────┴───────┘

Parameters:

  • other (Object) —

    Integer or boolean value; accepts expression input.

Returns:



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# File 'lib/polars/expr.rb', line 3707

def xor(other)
  self ^ other
end

#|(other) ⇒ Expr

Bitwise OR.

Returns:



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# File 'lib/polars/expr.rb', line 42

def |(other)
  _from_rbexpr(_rbexpr._or(_to_rbexpr(other)))
end