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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