module Distribution
  module Logistic
    module Ruby_
      class << self
        def rng(u,s)
          lambda {p_value(rand(),u,s)}
        end
        def pdf(x,u,s )
          (Math.exp(-(x-u) / s)) / (s*(1+Math.exp(-(x-u) / s)**2))
        end
        def cdf(x,u,s )
          1/(1+Math.exp(-(x-u) / s))
        end
        def p_value(pr,u,s )
          u+s*Math.log(pr/(1-pr))
        end
      end
    end
  end
end