Question

Hi huys : I want to map a “average” for all values in a map. say I have a list of maps :

[{"age" 2 "height" 1 "weight" 10},
{"age" 4 "height" 4 "weight" 20},
{"age" 7 "height" 11 "weight" 40}]

And my desired output is

{"age 5 "height" 5 ....}

///Below are the ramblings of my brain, i.e. the way I might imagine this working in Clojure…not to be taken too seriously

transpose the list :

  {"age" [2 4 7] "height" [1 4 11] } 

and then I could simply do something like (again, making up a function called freduce here)

  (freduce average (vals (map key-join list)))

to get

{"age" 5 "weight" 10 "height" 7}

Answer 1

Here’s a fairly verbose solution. Hopefully someone can come up with something better:

(let [maps [{"age" 2 "height" 1 "weight" 10},
            {"age" 4 "height" 4 "weight" 20},
            {"age" 7 "height" 11 "weight" 40}]
      ks (keys (first maps))
      series-size (count maps)
      avgs (for [k ks]
             (/ (reduce +
                        (for [m maps]
                          (get m k)))
                series-size))]
  (zipmap ks avgs))