Malthusian Growth Model in Ruby

I am interested in modeling a Malthusian growth model in Ruby. Does anyone have any ideas, or are there any interesting libraries that cover this? Any help is appreciated.

http://en.w开发者_如何学Pythonikipedia.org/wiki/Malthusian_growth_model

Do you really need a library for this?

p = 50
t = 5
r = 0.1
p *= Math.exp(r*t)
print p

If you want more, please be more specific.