From: ara.t.howard@...
Date: 2006-12-03T00:46:58+09:00
Subject: Re: [OT] calculations on lists of numbers

On Sat, 2 Dec 2006, Olivier wrote:

> Hi,
>
> 	I'm currently coding a ruby program for processing images. One of the class I
> wrote is intended to compute some stats about the luminance of a channel, but
> in fact it can be used on any set of numerical datas. The stats are :
> - an histogram
> - the mean
> - the variance
> - the deviation
> - the median
> - the skewness
> - the kurtosis
>
> 	It is very fast, since it uses no memory : the values are not stored
> internally, just the sub-results (so, a list of 2 values will use the same
> amount of memory than a list of a billion values), and also because the
> method that adds a value is generated depending of what stats you want to
> compute.
>
> 	It would be really easy to add min and max, but it would need one or two
> modifications to get rid of the "image-specific" things. Then, reading stdin
> and add the values would be no problem.
>
> 	If you want to base your work on my class then just tell me, I'll be happy to
> share it if it can help.
>
> -- Olivier

heh, i've got something similar i use to compute stats on binary data all the
time, here's the entire code

   harp:~> cat a.rb
   #! /dmsp/reference/bin/ruby

   require 'narray'
   require 'yaml'

   list = ARGF.readlines.map{|line| line.strip.split(%r/\s+/).map{|f| Float f}}.flatten
   na = NArray.to_na list

   puts '---'
   %w( min max mean median stddev ).each{|stat| puts "#{ stat }: #{ na.send stat}"}


but it's not as complete as yours.


-a
-- 
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