From: poopdeville / gmail.com [mailto:poopdeville / gmail.com] 
> first = [1,0,0,0,0]
> second = [1,1,0,0,0]
> third = [0,0,0,1,0]
> 
> I would end up with
> count = [2,1,0,1,0]

Built into Ruby:
irb(main):001:0> require 'matrix'
=> true
irb(main):002:0> first = Vector[1,0,0,0,0]
=> Vector[1, 0, 0, 0, 0]
irb(main):003:0> second = Vector[1,1,0,0,0]
=> Vector[1, 1, 0, 0, 0]
irb(main):004:0> third = Vector[0,0,0,1,0]
=> Vector[0, 0, 0, 1, 0]
irb(main):005:0> count = first + second + third
=> Vector[2, 1, 0, 1, 0]

However, I believe that's a pure-ruby implementation of matrices and
vectors. A quick bit of Googling looks ike RNum[1] might be crazy fast
and do what you need. I've never used it. I've also never used
NArray[2], but it might do what you need.

[1] http://rnum.rubyforge.org/
[2] http://narray.rubyforge.org/