Method: Axiom::Aggregate::Variance.call

Defined in:
lib/axiom/aggregate/variance.rb

.call(accumulator, value) ⇒ Array(Integer, Numeric, Numeric)

Return the count, mean, and sum of squares for a sequence of numbers

Examples:

count, mean, sum_of_squares = Variance.call(accumulator, value)

Parameters:

  • accumulator (Array(Integer, Numeric, Float))
  • value (Numeric)

Returns:

  • (Array(Integer, Numeric, Numeric)) 


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# File 'lib/axiom/aggregate/variance.rb', line 23

def self.call(accumulator, value)
  return accumulator if value.nil?
  mean, sum_of_squares  = accumulator.last(2)
  delta                 = mean.nil? ? value : value - mean
  count, new_mean       = Mean.call(accumulator, value)
  sum_of_squares       += delta * (value - new_mean)
  [ count, new_mean, sum_of_squares ]
end