Hi Jim,
I don't think that would give the result I need. Let me give a more
realistic example:
(defn every-day [[start :start end: end]] ...) ; returns [date1 date2 date3]
(def m [{:id 1 :start 1/1/2010 :end 3/1/2010} {:id 2 :start 3/1/2010 :end
3/1/2010}]
(group-by every-day m) would give something like:
{[1/1/2010 2/1/2010 3/1/2010] [{:id1 ...}]
[3/1/2010] [{:id 2...}]}
I now want to transform that result to the following:
{1/1/2010 [{:id 1...}]
3/1/2010 [{:id 1 ...} {:id 3}]}
I am thinking I probably need to process each key/value in the original map
(m) and then use assoc-in to build up the map but that feels pretty
imperative and given Clojure's magic and transforming shapes I figure there
must be a better way...
On 8 July 2013 20:35, Jim - FooBar(); <[email protected]> wrote:
> you can use group-by as you showed and then reduce-kv over them map
> replacing each key with '(count key)'...I don't see a way of doing this in
> one-pass using group-by alone...
>
> Jim
>
>
>
> On 08/07/13 20:25, Colin Yates wrote:
>
>> Hi,
>>
>> I have a sequence of items and want to group them into categories, the
>> value of which is a function of the item. This sounds exactly what
>> group-by is after.
>>
>> The kicker is that the function could return multiple values. Imagine
>> each item was a date range and I wanted to group them by the number of days
>> in that date range.
>>
>> For example, (group-by #(range 1 (inc %)) [1 2 3] => {(1) [1] (1 2) [2]
>> (1 2 3) [3]}. I want {1 [1] 2 [1 2] 3 [1 2 3]}.
>>
>> Any ideas?
>>
>> Thanks!
>>
>> Col
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