Robert Klemme wrote:
> On 01/06/2010 03:56 PM, Ralf Mueller wrote:
>> Robert Klemme wrote:
>>> On 01/06/2010 09:45 AM, Kolya17 Kolya17 wrote:
>>>> Hi!
>>>>
>>>> I have a two-dimensional array Farr.
>>>>
>>>> Farr.each{ |i| print i}
>>>>
>>>> output:
>>>> ["200912-829", 9]
>>>> ["200912-893", 3]
>>>> ["200912-893", 5]
>>>> ["200912-829", 1]
>>>> ["200911-818", 6]
>>>> ["200911-893", 1]
>>>> ["200911-827", 2]
>>>>
>>>> I'm trying to get another two-dimensional array, which would be the
>>>> grouping of the first elements.
>>>> In SQL it would be so:
>>>>
>>>> select String, sum(Number)
>>>> from Farr
>>>> group by String
>>>>
>>>> and the resulting array would:
>>>> ["200912-829", 10]
>>>> ["200912-893", 8]
>>>> ["200911-818", 6]
>>>> ["200911-893", 1]
>>>> ["200911-827", 2]
>>>>
>>>> Help please.
>>>> I apologize for spelling, English is not my native.
>>> There is actually Array#group_by since 1.8.7:
>>>
>>> arr.group_by {|date,val| date}.each do |date, items|
>>>   printf "%-20s %6d\n", date, items.inject(0) {|sum,x|sum+x}, "\n"
>>> end
>>>
>> Looks good, but I could not find it in the online documentation on 
>> ruby-doc.org? (Array,Enumerable)
>
> That's weird.  I found it immediately:
>
> group_by
> http://ruby-doc.org/core-1.8.7/classes/Enumerable.html#M001150
>
> inject
> http://ruby-doc.org/core-1.8.7/classes/Enumerable.html#M001147
>
thanks robert!
I've always used ruby-doc.org/core for getting the latest 1.8 doc. 
Didn't recognized, it belongs to 1.8.6 instead of the more recent 1.8.7...

regards
ralf