[SOLVED] Generate Array of Numbers that fit to a Probability Distribution in Ruby?

Generate Array of Numbers that fit to a Probability Distribution in Ruby?

Say I have 100 records, and I want to mock out the created_at date so it fits on some curve. Is there a library to do that, or what formula could I use? I think this is along the same track:

Generate Random Numbers with Probabilistic Distribution

I don't know much about how they are classified in mathematics, but I'm looking at things like:

bell curve
logarithmic (typical biology/evolution) curve? ...

Just looking for some formulas in code so I can say this:

Given 100 records, a timespan of 1.week, and an interval of 12.hours
set created_at for each record such that it fits, roughly, to curve

Thanks so much!

Update

I found this forum post about ruby algorithms, which led me to rsruby, an R/Ruby bridge, but that seems like too much.

Update 2

I wrote this little snippet trying out the gsl library, getting there...

Generate test data in Rails where created_at falls along a Statistical Distribution

Solution

You can generate UNIX timestamps which are really just integers. First figure out when you want to start, for example now:

start = DateTime::now().to_time.to_i

Find out when the end of your interval should be (say 1 week later):

finish = (DateTime::now()+1.week).to_time.to_i

Ruby uses this algorithm to generate random numbers. It is almost uniform. Then generate random numbers between the two:

r = Random.new.rand(start..finish)

Then convert that back to a date:

d = Time.at(r)

This looks promising as well: http://rb-gsl.rubyforge.org/files/rdoc/randist_rdoc.html

And this too: http://rb-gsl.rubyforge.org/files/rdoc/rng_rdoc.html