module Enumerable - sixarm_ruby_math_statistics-2.0.0 Documentation

deviation() click to toggle source

Calculate the deviation of a list of numbers.

Example:

[3, 1, 4].deviation => 1.247

# File lib/sixarm_ruby_math_statistics/enumerable.rb, line 82
def deviation
  size==0 ? nil : Math::sqrt(variance)
end

mean() click to toggle source

Calculate the mean of a list of numbers.

Example:

[3, 1, 4].mean => 2.666

If the list is blank, then return nil.

# File lib/sixarm_ruby_math_statistics/enumerable.rb, line 40
def mean
  size==0 ? nil : sum.to_f / size
end

median() click to toggle source

Calculate the median of a list of numbers.

Example:

[3, 1, 4].median => 3.0

If the list is blank, then return nil.

# File lib/sixarm_ruby_math_statistics/enumerable.rb, line 52
def median
  size==0 ? nil : ((0==self.size%2) ? sort[size/2-1,2].mean : sort[self.size/2].to_f)
end

sum(identity = 0, &block) click to toggle source

Calculate the sum of a list of numbers.

Example:

[3, 1, 4].sum => 8

Example with a block:

[3, 1, 4].sum{|x| x * 2} => 16

Example with a default value in case the list is empty:

[].sum(99) => 99

This method is copied from rails to ensure compatibility.

# File lib/sixarm_ruby_math_statistics/enumerable.rb, line 23
def sum(identity = 0, &block)
  return identity unless size > 0
  if block_given?
    map(&block).sum
  else
    inject { |sum, element| sum + element }
  end
end

sum_of_squares() click to toggle source

Calculate the sum of squares of a list of numbers.

Example:

[3, 1, 4].sum_of_squares => 26

# File lib/sixarm_ruby_math_statistics/enumerable.rb, line 62
def sum_of_squares
  size==0 ? 0 : inject(0){|sum,x|sum+(x*x)}
end

variance() click to toggle source

Calculate the variance of a list of numbers.

Example:

[3, 1, 4].variance => 1.555

# File lib/sixarm_ruby_math_statistics/enumerable.rb, line 72
def variance
  size==0 ? nil : ( m=mean and sum_of_squares.to_f/size - m*m )
end