Thanks BG, I prefer your version. I'd forgotten about select-keys.
Cheers,
David
On 4 April 2012 15:20, Baishampayan Ghose <b.gh...@gmail.com> wrote:
>> Please have a look at the following function (explained in the doc
>> string). I have a bunch of rows that I need to aggregate using
>> different functions per field. I also need to apply the aggregate to a
>> subset of the rows. Obviously this is just like SQL aggregation, hence
>> the interface I've specified.
>>
>> However I'm left wondering whether my implementation could be improved.
>>
>> Particularly I very often find myself doing
>>
>> (apply hash-map (flatten (for [[k v] some-map] ...)))
>>
>> so often in fact that I feel like I'm missing something.
>>
>> Any pointers or advice on improving my style will be much appreciated!
>
> Don't have a direct answer to your question, but what about
> implementing aggregate like this -
>
> (defn aggregate [rows & {select :select where :where}]
> (let [projection (apply merge-with vector (map #(select-keys %
> (keys select)) (filter where rows)))]
> (reduce (fn [agg [k v]] (assoc agg k (apply (select k) v))) {}
> projection)))
>
> Regards,
> BG
>
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> Baishampayan Ghose
> b.ghose at gmail.com
>
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David Jagoe
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