You can use uniform random numbers generated from the GNU Scientific
library, via ruby-gsl,

http://rb-gsl.rubyforge.org/,

see : http://rb-gsl.rubyforge.org/rng.html,

if you should want random numbers that follow some other distribution,
you can always pick a random number in the interval [0,1] and then
numerically find the position at which the cumulative distribution
reaches this value. Do this many times .. this gives you a distribution
of points according to the distribution you're looking for.
You don't have to program it all by yourself, but you can use
the statistics2 package by Shin-ichiro Hara: see the readme here:

http://blade.nagaokaut.ac.jp/~sinara/ruby/math/statistics2/statistics2-0.50/README

Best regards,

Axel 
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