From: "David A. Black" <dblack@...>
Date: 2007-08-24T22:33:30+09:00
Subject: Re: Combining Array Elements

Hi --

On Fri, 24 Aug 2007, Jeremy Wells wrote:

> gregarican wrote:
>> I have an array that I would like to combine elements. Here's a sample
>> array:
>> 
>> [["Value A", "Value B", 3], ["Value A", "Value C", 2],["Value A",
>> Value B", 1]]
>> 
>> What I would like to do is find the elements where the first two items
>> are the same and then combine the third. The resulting array would
>> consist of:
>> 
>> [["Value A", "Value B", 4],["Value A", "Value C", 2]]
>> 
>> This is something that is out in left field in terms of how I've used
>> arrays in the past. Anyone know of a quick bit of script I can whip up
>> that will suit the task?
>> 
> new_array = array.collect{|v| [v[0],v[1], a.select{|b| b[0] == v[0] && b[1]
                                             ^^^^^^^^
You mean array.select, I think.

> == v[1] }.inject(0){|m,b| m + b.last}]}.uniq

This is just a cosmetic change, but you could do:

new_array = array.map {|v,w| [v,w, array.select {|b,c|
   b == v && c == w }.inject(0){|m,b| m + b.last}]}.uniq

or even:

new_array = array.map {|v,w| [v,w, array.select {|b,c|
   [b,c] == [v,w] }.inject(0){|m,b| m + b.last}]}.uniq


David

-- 
* Books:
   RAILS ROUTING (new! http://www.awprofessional.com/title/0321509242)
   RUBY FOR RAILS (http://www.manning.com/black)
* Ruby/Rails training
     & consulting:  Ruby Power and Light, LLC (http://www.rubypal.com)