From: "Hal E. Fulton" <hal9000@...>
Date: 2003-03-29T20:09:24+09:00
Subject: Re: Weighted random selection -- how would you do this?

----- Original Message ----- 
From: "Daniel Carrera" <dcarrera@math.umd.edu>
To: "ruby-talk ML" <ruby-talk@ruby-lang.org>
Sent: Saturday, March 29, 2003 12:31 AM
Subject: Re: Weighted random selection -- how would you do this?


> Say that you have a hash 'events' whose keys are the events you are 
> interested in and the values are the corresponding weights:
> 
> e.g.
> events = { 
> "event1" => 5, 
> "event2" => 17, 
> "event3" => 6, 
> "event4" => 13
> }
> 
> Solution:
> tot = 0; events.each { |event, weight| tot += weight }
> val = rand tot
> event = events.each do |event, weight|
> val -= weight; 
> return event if val < 0
> end
> 
> This should work, I think.

Does indeed, thank you. The algorithm is 
a little non-obvious to me, but it is 
simpler than mine.

Hal