• clojure
• java

# min-key

## clojure.core

• (min-key k x)
• (min-key k x y)
• (min-key k x y & more)
Returns the x for which (k x), a number, is least.

### 2 Examples top

• ```;; we have a list of key colours
;; We want to find the one closest to a supplied colour
;; We're storing rgb values as [r g b]
;; use min-key to find colour that minimizes
;; the euclidean distance between the supplied colour
;; and each key colour
;; thanks to rhudson, raek and mfex on #clojure

(defn distance-squared [c1 c2]
"Euclidean distance between two collections considered as coordinates"
(->> (map - c1 c2) (map #(* % %)) (reduce +)))

(def key-colours
{[224 41 224] :purple
[24 180 46] :green
[12 129 245] :blue
[254 232 23] :yellow
[233 233 233] :white
[245 27 55] :red
[231 119 41] :orange
})

(defn rgb-to-key-colour
"Find colour in colour map closest to the supplied [r g b] triple"
[rgb-triple colour-map]
(colour-map
(apply min-key (partial distance-squared rgb-triple) (keys colour-map))))

user=> (rgb-to-key-colour [255 0 0] key-colours)
:red
```
• ```; "min-key"/"max-key" to "min"/"max" like "sort-by" to "sort"
(min-key #(Math/abs %) -3 1 4)
; 1

(apply min-key #(Math/abs %) [-3 1 4])
; 1
```

### Source clojure/core.clj:4404 top

```(defn min-key
"Returns the x for which (k x), a number, is least."