From: Ne Scripter <stuart.clarke@...>
Date: 2009-09-30T02:40:24+09:00
Subject: Re: Group by unique entries of a hash

So if we were to take this further.We now have out hashMapping list

"2efa4ba470",  "00000005""00000004"
"c0784b5de101",  "00000006""00000003"
"02adecfd5c",  "00000002"
"c0784b5de101",  "00000001"

Now we split the hash to give only the ID values (column 2) again doing 
some like this:

hashMapping.each do |itemDetail|
 newID = itemDetail[1].to_s.delete("\"").strip
end

I have another declared array in my code, with many more ID values like 
those shown above

moreIDs = ["00000001", "00000003", "00000004", "00000005", 00000007", 
"00000008"]

What I want to is search for all newID's that match moreIDs and output 
the matching ID and the corresponding code shown in column one. So the 
sample output would be like this:

"2efa4ba470",  "00000005""00000004"
"c0784b5de101",  "00000003"
"c0784b5de101",  "00000001"

Show this shows the string code for an ID that is present in both of my 
lists. I had thought something like moreID == newID but that creates a 
lot off do loops. Also, thr though of array intersects crossed my mind, 
but we have a hash and array hear so I was unsure of how to make this 
work?

Any assistance in greatly appreciated.

Ne Scripter wrote:
> Ah yes, that makes perfect sense.
> 
> Thanks
> 
> Paul Smith wrote:
> 
>> 
>> You want a hash where the key is the element you want to group on, and
>> the 'item' is an array of all items with the shared key.  A bit like
>> (untested):
>> 
>> hashMapping = {}
>> 
>> IO.foreach(source.to_s) do |data|
>>    fields = data.split(",")
>>    hash = fields[0]
>>    ocrID = fields[1]
>> 
>>    hashMapping[ocrID] ||= [] #If hashMapping has never seen this key
>> before, make an empty array
>> 
>>    hashMapping[ocrID] << hash #Add the new element to the array for this 
>> key
>> 
>>  end
>> 
>>>
>>> Many thanks
>>> --
>>> Posted via http://www.ruby-forum.com/.
>>>
>>>
> 
>> --
>> Paul Smith
>> http://www.nomadicfun.co.uk
>> 
>> paul@pollyandpaul.co.uk

-- 
Posted via http://www.ruby-forum.com/.