Contents

# -*- coding: utf-8 -*-
=begin rdoc
Please see README
=end


module Enumerable


  # Examples
  #   [].sum => 0
  #   [1].sum => 1
  #   [1,2,3].sum => 5
  #
  # Example with default for empty
  #   [].sum(99) => 99
  #
  # Example with block
  #   [1,2,3].sum{|x| x*2} => 10
  #
  # This method is copied from rails to ensure compatibility.
  
  def sum(identity = 0, &block)
    return identity unless size > 0
    if block_given?
      map(&block).sum
    else
      inject { |sum, element| sum + element }
    end
  end


  # Examples
  #   [].mean => nil
  #   [1].mean => 1.0
  #   [1,2].mean => 1.5
  #   [1,2,9].mean => 4.0
  
  def mean
    size==0 ? nil : sum.to_f / size
  end


  # Examples
  #  [].median => nil
  #  [1].median => 1.0
  #  [1,2].median => 1.5
  #  [1,2,9].mean => 2.0
  
  def median
    size==0 ? nil : ((0==self.size%2) ? sort[size/2-1,2].mean : sort[self.size/2].to_f)
  end
  

  # Examples
  #  [].sum_of_squares => 0
  #  [1].sum_of_squares => 1.0
  #  [1,2].sum_of_squares => 5.0
  #  [1,2,3].sum_of_squares => 14.0
  
  def sum_of_squares
    size==0 ? 0 : inject(0){|sum,x|sum+(x*x)}
  end
  

  # Examples
  #   [].variance => nil
  #   [1].variance =>  0.0
  #   [1,2].variance => 0.25
  #   [1,2,3,4].variance => 1.25
  
  def variance
    size==0 ? nil : ( m=mean and sum_of_squares.to_f/size - m*m )
  end
  
  
  # Examples
  #   [].deviation => nil
  #   [1].deviation => 0.0
  #   [1,2].deviation => 0.5
  #   [2,2,4,2,2].deviation => 0.8
  
  def deviation
    size==0 ? nil : Math::sqrt(variance)
  end

end

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
sixarm_ruby_math_statistics-1.2.0	lib/sixarm_ruby_math_statistics.rb