I would write like this
(defn sum-by-type [coll]
(->> coll
(map (fn [ {v "Value" t "Type" } ] {t (read-string v) }))
(apply (partial merge-with +))))
If the map keyword based, it will be simpler than above
(defn sum-by-type [coll]
(->> coll
(map (fn [ {v :value t :type } ] {t v}))
(apply (partial merge-with +)))
Jestan Nirojan.
On Oct 15, 12:46 am, Dave Ray <dave...@gmail.com> wrote:
> Someone cleverer than me to post the built-in function that already
> does exactly what you want, but here's one way:
>
> (defn sum-by-type [in]
> (->> in
> (group-by #(get % "Type"))
> (map
> (fn [[k vs]]
> {"Type" k
> "Value" (reduce
> (fn [acc v] (+ acc (Double/parseDouble (get v "Value"))))
> 0
> vs)}))))
>
> All the strings don't help much.
>
> Cheers,
>
> Dave
>
>
>
>
>
>
>
> On Fri, Oct 14, 2011 at 1:25 PM, der <derealme.derea...@gmail.com> wrote:
> > Hi,
>
> > I'm a Clojure newbie trying to the following simple task:
>
> > Given a list of maps of the followign format: ({"Type" "A", "Value"
> > "5"} {"Type" "B", "Value" "4"} {"Type" "A", "Value" "7.2"} {"Type"
> > "A", "Value" "25.4"} {"Type" "B", "Value" "2.982"})
>
> > I want to compute a list of maps such that each type appears once in
> > the list and the value of the type is the sum of the values, so that
> > in the example it would be:
>
> > ({"Type", "A", "Value", "37.6"} {"Type", "B", "Value", "6.982"})
>
> > Any ideas?
>
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