daru

Daru::DataFrame#pivot_table

Pivots a data frame on specified vectors and applies an aggregate function
to quickly generate a summary.

== Options

+:index+ - Keys to group by on the pivot table row index. Pass vector names
contained in an Array.

+:vectors+ - Keys to group by on the pivot table column index. Pass vector
names contained in an Array.

+:agg+ - Function to aggregate the grouped values. Default to *:mean*. Can
use any of the statistics functions applicable on Vectors that can be found in
the Daru::Statistics::Vector module.

+:values+ - Columns to aggregate. Will consider all numeric columns not
specified in *:index* or *:vectors*. Optional.

== Usage

  df = Daru::DataFrame.new({
    a: ['foo'  ,  'foo',  'foo',  'foo',  'foo',  'bar',  'bar',  'bar',  'bar'],
    b: ['one'  ,  'one',  'one',  'two',  'two',  'one',  'one',  'two',  'two'],
    c: ['small','large','large','small','small','large','small','large','small'],
    d: [1,2,2,3,3,4,5,6,7],
    e: [2,4,4,6,6,8,10,12,14]
  })
  df.pivot_table(index: [:a], vectors: [:b], agg: :sum, values: :e)

  #=>
  # #<Daru::DataFrame:88342020 @name = 08cdaf4e-b154-4186-9084-e76dd191b2c9 @size = 2>
  #            [:e, :one] [:e, :two]
  #     [:bar]         18         26
  #     [:foo]         10         12

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