Methods to calculate the mean, median and mode of an array.

averageable.rb

module Averageable
  def mean(&block)
    sum(&block) / length.to_f
  end
  
  def count(elem)
    length - (self - [elem]).length
  end
  
  def mode
    max { |a, b| count(a) <=> count(b) }
  end
  
  def median
    sorted = sort
    index = (length / 2) - 1
    if length_odd?
      sorted[index + 1]
    else
      (sorted[index] + sorted[index + 1]) / 2.0
    end
  end
  
  def length_even?
    (length % 2).zero?
  end
  
  def length_odd?
    !length_even?
  end
  
  # From ActiveSupport.
  def sum(identity = 0, &block)
    return identity unless size > 0
    
    if block_given?
      map(&block).sum
    else
      inject { |sum, element| sum + element }
    end
  end unless method_defined?(:sum)
end