How to Increment Values in a Map

(def my-map {:a 1 :b 2})
(zipmap (keys my-map) (map inc (vals my-map)))
;;=> {:b 3, :a 2}

To update only one value by key:

(update-in my-map [:b] inc) ;;=> {:a 1, :b 3}

Since Clojure 1.7 it's also possible to use update:

(update my-map :b inc)

Just produce a new map and use it:

(def m {:a 3 :b 4})

(apply merge 
  (map (fn [[k v]] {k (inc v) }) m))

; {:b 5, :a 4}

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