Contents

class Array
  def variance
    mean = self.mean

    (1.0 / self.length) * self.map{|x| (x - mean) ** 2}.inject(:+)
  end

  def standard_deviation
    Math.sqrt(self.variance)
  end

  def std_dev
    self.standard_deviation
  end

  def coefficient_of_variation
    self.standard_deviation / self.mean
  end
end

Version data entries

2 entries across 2 versions & 1 rubygems

Version	Path
rstat-0.0.4	lib/rstat/core_ext/array/standard_deviation.rb
rstat-0.0.3	lib/rstat/core_ext/array/standard_deviation.rb