Class: Rubyvis::Nest
Overview
Represents a Nest operator for the specified array. Nesting allows elements in an array to be grouped into a hierarchical tree structure. The levels in the tree are specified by key functions. The leaf nodes of the tree can be sorted by value, while the internal nodes can be sorted by key. Finally, the tree can be returned either has a multidimensional array via Nest.entries, or as a hierarchical map via Nest.map. The Nest.rollup routine similarly returns a map, collapsing the elements in each leaf node using a summary function.
For example, consider the following tabular data structure of Barley yields, from various sites in Minnesota during 1931-2:
{ yield: 27.00, variety: "Manchuria", year: 1931, site: "University Farm" },
{ yield: 48.87, variety: "Manchuria", year: 1931, site: "Waseca" },
{ yield: 27.43, variety: "Manchuria", year: 1931, site: "Morris" }
To facilitate visualization, it may be useful to nest the elements first by year, and then by variety, as follows:
var nest = Rubyvis.nest(yields)
.key(lambda {|d| d.year})
.key(lambda {|d| d.variety})
.entries();
This returns a nested array. Each element of the outer array is a key-values pair, listing the values for each distinct key:
<pre>{ key: 1931, values: [
{ key: "Manchuria", values: [
{ yield: 27.00, variety: "Manchuria", year: 1931, site: "University Farm" },
{ yield: 48.87, variety: "Manchuria", year: 1931, site: "Waseca" },
{ yield: 27.43, variety: "Manchuria", year: 1931, site: "Morris" },
...
] },
{ key: "Glabron", values: [
{ yield: 43.07, variety: "Glabron", year: 1931, site: "University Farm" },
{ yield: 55.20, variety: "Glabron", year: 1931, site: "Waseca" },
...
] },
] },
{ key: 1932, values: … }</pre>
Further details, including sorting and rollup, is provided below on the corresponding methods.
Instance Attribute Summary collapse
-
#array ⇒ Object
Returns the value of attribute array.
-
#keys ⇒ Object
Returns the value of attribute keys.
-
#order ⇒ Object
Returns the value of attribute order.
Instance Method Summary collapse
-
#entries ⇒ Object
Returns a hierarchical nested array.
- #entries_entries(map) ⇒ Object
- #entries_sort(array, i) ⇒ Object
-
#initialize(array) ⇒ Nest
constructor
Constructs a nest operator for the specified array.
- #key(k) ⇒ Object
-
#map ⇒ Object
Returns a hierarchical map of values.
- #rollup(f) ⇒ Object
- #rollup_rollup(map, f) ⇒ Object
- #sort_keys(order = nil) ⇒ Object
- #sort_values(order = nil) ⇒ Object
Constructor Details
#initialize(array) ⇒ Nest
Constructs a nest operator for the specified array. This constructor should not be invoked directly; use Rubyvis.nest instead.
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# File 'lib/rubyvis/nest.rb', line 76 def initialize(array) @array=array @keys=[] @order=nil end |
Instance Attribute Details
#array ⇒ Object
Returns the value of attribute array.
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# File 'lib/rubyvis/nest.rb', line 71 def array @array end |
#keys ⇒ Object
Returns the value of attribute keys.
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# File 'lib/rubyvis/nest.rb', line 71 def keys @keys end |
#order ⇒ Object
Returns the value of attribute order.
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# File 'lib/rubyvis/nest.rb', line 71 def order @order end |
Instance Method Details
#entries ⇒ Object
Returns a hierarchical nested array. This method is similar to pv.entries, but works recursively on the entire hierarchy. Rather than returning a map like #map, this method returns a nested array. Each element of the array has a key
and values
field. For leaf nodes, the values
array will be a subset of the underlying elements array; for non-leaf nodes, the values
array will contain more key-values pairs.
<p>For an example usage, see the Nest constructor.
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# File 'lib/rubyvis/nest.rb', line 148 def entries() entries_sort(entries_entries(map),0) end |
#entries_entries(map) ⇒ Object
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# File 'lib/rubyvis/nest.rb', line 151 def entries_entries(map) array=[] map.each_pair {|k,v| array.push(NestedArray.new({:key=>k, :values=>(v.is_a? Array) ? v: entries_entries(v)})) } array end |
#entries_sort(array, i) ⇒ Object
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# File 'lib/rubyvis/nest.rb', line 158 def entries_sort(array,i) o=keys[i].order if o array.sort! {|a,b| o.call(a.key, b.key)} end i+=1 if (i<keys.size) array.each {|v| entries_sort(v, i) } end array end |
#key(k) ⇒ Object
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# File 'lib/rubyvis/nest.rb', line 81 def key(k) @keys.push(k) return self end |
#map ⇒ Object
Returns a hierarchical map of values. Each key adds one level to the hierarchy. With only a single key, the returned map will have a key for each distinct value of the key function; the correspond value with be an array of elements with that key value. If a second key is added, this will be a nested map. For example:
<pre>Rubyvis.nest(yields)
.key(function(d) d.variety)
.key(function(d) d.site)
.map()</pre>
returns a map m
such that m[variety][site]
is an array, a subset of yields
, with each element having the given variety and site.
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# File 'lib/rubyvis/nest.rb', line 109 def map #i=0 map={} values=[] @array.each_with_index {|x,j| m=map (@keys.size-1).times {|i| k=@keys[i].call(x) m[k]={} if (!m[k]) m=m[k] } k=@keys.last.call(x) if(!m[k]) a=[] values.push(a) m[k]=a end m[k].push(x) } if(self.order) values.each_with_index {|v,vi| values[vi].sort!(&self.order) } end map end |
#rollup(f) ⇒ Object
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# File 'lib/rubyvis/nest.rb', line 199 def rollup(f) rollup_rollup(self.map, f) end |
#rollup_rollup(map, f) ⇒ Object
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# File 'lib/rubyvis/nest.rb', line 172 def rollup_rollup(map,f) map.each_pair {|key,value| if value.is_a? Array map[key]=f.call(value) else rollup_rollup(value,f) end } return map; end |
#sort_keys(order = nil) ⇒ Object
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# File 'lib/rubyvis/nest.rb', line 85 def sort_keys(order=nil) keys[keys.size-1].order = order.nil? ? Rubyvis.natural_order : order return self end |
#sort_values(order = nil) ⇒ Object
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# File 'lib/rubyvis/nest.rb', line 89 def sort_values(order=nil) @order = order.nil? ? Rubyvis.natural_order : order return self end |