Method: Polars::Selectors.string

Defined in:

lib/polars/selectors.rb

.string(include_categorical: false) ⇒ Selector

Select all String (and, optionally, Categorical) string columns.

df.group_by(Polars.cs.string).agg(Polars.cs.numeric.sum).sort(Polars.cs.string) shape: (2, 3) ┌─────┬─────┬─────┐ │ w ┆ x ┆ y │ │ --- ┆ --- ┆ --- │ │ str ┆ i64 ┆ f64 │ ╞═════╪═════╪═════╡ │ xx ┆ 0 ┆ 2.0 │ │ yy ┆ 6 ┆ 7.0 │ └─────┴─────┴─────┘

Examples:

df = Polars::DataFrame.new(
  {
    "w" => ["xx", "yy", "xx", "yy", "xx"],
    "x" => [1, 2, 1, 4, -2],
    "y" => [3.0, 4.5, 1.0, 2.5, -2.0],
    "z" => ["a", "b", "a", "b", "b"]
  },
).with_columns(
  z: Polars.col("z").cast(Polars::Categorical.new("lexical")),
)

Group by all string columns, sum the numeric columns, then sort by the string cols:

Group by all string and categorical columns:

df.group_by(Polars.cs.string(include_categorical: true)).agg(Polars.cs.numeric.sum).sort(
  Polars.cs.string(include_categorical: true)
)
# =>
# shape: (3, 4)
# ┌─────┬─────┬─────┬──────┐
# │ w   ┆ z   ┆ x   ┆ y    │
# │ --- ┆ --- ┆ --- ┆ ---  │
# │ str ┆ cat ┆ i64 ┆ f64  │
# ╞═════╪═════╪═════╪══════╡
# │ xx  ┆ a   ┆ 2   ┆ 4.0  │
# │ xx  ┆ b   ┆ -2  ┆ -2.0 │
# │ yy  ┆ b   ┆ 6   ┆ 7.0  │
# └─────┴─────┴─────┴──────┘

Returns:

• (Selector)

# File 'lib/polars/selectors.rb', line 1841

def self.string(include_categorical: false)
  string_dtypes = [String]
  if include_categorical
    string_dtypes << Categorical
  end

  by_dtype(string_dtypes)
end