I didn't see this original email for some reason, but here's a
simplified version:
(reduce
(fn [coll {a1 :a1 :as value}] (update-in coll [a1] conj value))
{}
data)
This takes advantage of update-in passing nil if it doesn't have the
key and conj with nil returning a seq of one value.
On Sun, Apr 17, 2011 at 12:30 AM, Shoeb Bhinderwala <[email protected]> wrote:
> Wrote the following function which did the trick:
>
> (defn partn [data]
> (let
> [add-mapping
> (fn [m v]
> (assoc m v (filter #(= v (:a1 %)) data)))]
> (reduce add-mapping {} (set (map #(:a1 %) data))))
>
> On Sat, Apr 16, 2011 at 8:15 PM, shuaybi <[email protected]> wrote:
>>
>> I am trying to write a function but can't get it right. I need to loop
>> through my data records and for each unique value of :a1 I need to
>> partition the data and create a resulting map so that the key is value
>> of :a1 and the associated value of this key is all records with that
>> value of :a1. Better explained with code, where given the definition
>> of data below, I need to write a function that will return the
>> definition of "result" below.
>>
>> ;data is a list of records (maps)
>> (def data '({:a1 2 :a2 34 :a3 76 :a4 87},
>> {:a1 3 :a2 30 :a3 38 :a4 39},
>> {:a1 2 :a2 67 :a3 32 :a4 38},
>> {:a1 4 :a2 47 :a3 73 :a4 38},
>> {:a1 3 :a2 84 :a3 86 :a4 63}))
>>
>> ;result should be a map, keyed by unique values of :a1 and containing
>> all records for that value of :a1
>> (def result '{2 ({:a1 2 :a2 34 :a3 76 :a4 87}, {:a1 2 :a2 67 :a3
>> 32 :a4 39}), ;list of records where :a1 = 2
>> 3 ({:a1 3 :a2 30 :a3 38 :a4 39}, {:a1 3 :a2 84 :a3
>> 86 :a4 63}), ;list of records where :a1 = 3
>> 4 ({:a1 4 :a2 47 :a3 73 :a4 38}) ;list of records
>> where :a1 = 4
>> })
>>
>> (defn get-val-a1
>> "Return all records in data where :a1 is specified val"
>> [data val]
>> (filter
>> #(= val (:a1 %)) ;filter function
>> data))
>>
>> (defn unique-a1
>> "Get set of all unique :a1 values"
>> [m]
>> (set (map #(:a1 %) m)))
>>
>> ;This is the function I am trying to write but can't get it right.
>> (defn partn [data]
>> (let [val-set (unique-a1 data)) ;get unique :a1 values
>> ret-val {}]
>> (loop [v val-set] ;loop through the unique values
>> (assoc ret-val v (get-val-a1 data v))) ;build final map
>> ret-val))
>>
>>
>
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