正規分布を求めるクラス。

ndist.rb

#!/bin/ruby
# -*- encoding: shift_jis -*-


class GaussianDistribution
  def initialize(mu = 0, sigma = 1)
    @mu = mu.to_f
    @sigma = sigma.to_f
  end


  def average
    @mu
  end


  def distributed
    @sigma ** 2
  end


  def prob(x)
    1 / Math.sqrt( 2 * Math::PI * @sigma ) * Math.exp( -( (x - average) ** 2 / (2 * distributed) ) )
  end
end

if __FILE__ == "ndist.rb" then
  gd = GaussianDistribution.new
  ( -5.0..5.0 ).step( 0.1 ) do |x|
    printf( "%.2f,%0.7f\n", x, gd.prob( x ) )
  end
end

# file: ndist.rb