From: Kalman Noel <invalid@...>
Date: 2007-02-20T19:20:07+09:00
Subject: Re: Help with Class design

Chris Lowis:
> require 'mathn'
> 
> class MySignal
> 
>   def initialize(input)
>     @signal = input
>   end
> 
>   def mean()
>     sum = 0;
>     @signal.each {|i| sum+=i}
>     mean = sum/@signal.length
>   end
> 
>   def variance()
>     m = @signal.mean
>     var = @signal.inject(0) { |var, x| var += (x - m) ** 2 }
>     var = var/(@signal.length-1)
>   end
> end

I suppose that you variance method should read something like

   def variance
      m = mean
      @signal.inject(0) { |sum, x| sum + (x-m)**2 } / @signal.length
   end

Note that I prefer not using meaningless assignment in the inject block.

Kalman