From: Olivier Renaud <o.renaud@...>
Date: 2007-03-26T02:00:00+09:00
Subject: Re: splitting an array into sub_arrays ...need advice

Le dimanche 25 mars 2007 17:50, Josselin a �crit�:
> I have an array similar to this example  (after sorting it on a[i][1]
> and a[i][2])
>
> start_array = [ [1, 1, 1, 0], [2, 1, 1, 0], [3, 1, 1, 0], [4, 1, 2, 0],
> [5, 1, 2, 0], [6, 2, 1, 0], [7, 2, 1, 0], [8, 2, 2, 0], [9, 2, 2, 0],
> [10, 2, 3, 0] ]
>
> I am trying to split it, into sub_arrays according to similarelements
> a[i][1] and a[i][2] ,
> to get another array like this one :
>
> resulting_array = [  [[1, 1, 1, 0], [2, 1, 1, 0], [3, 1, 1, 0]]  ,
> [[4, 1, 2, 0], [5, 1, 2, 0]]  ,  [[6, 2, 1, 0], [7, 2, 1, 0]]  , [[8,
> 2, 2, 1], [9, 2, 2, 0]]  , [[10, 2, 3, 0]]   ]

There is a way to group objects easily with Enumerable#partition_by, in the 
Facets gem.

irb(main):001:0> require 'facets'
irb(main):002:0> require 'enumerable/partition_by'
irb(main):006:0> start_array.partition_by {|ary| ary[1..2]}
=> {[1, 2]=>[[4, 1, 2, 0], [5, 1, 2, 0]], [2, 1]=>[[6, 2, 1, 0], [7, 2, 1, 
0]], [1, 1]=>[[1, 1, 1, 0], [2, 1, 1, 0], [3, 1, 1, 0]], [2, 3]=>[[10, 2, 3, 
0]], [2, 2]=>[[8, 2, 2, 0], [9, 2, 2, 0]]}

It may help you for what you are trying to do.

-- 
Olivier Renaud