12  Median

for odd number of elements

(def numbers [1 2 3])

numbers

[1 2 3]

(nth numbers (/ (count numbers) 2))

2

for even number of elements

(def numbers [1 2 3 4])

numbers

[1 2 3 4]

(count numbers)

4

(/ (count numbers) 2)

2

(nth numbers (/ (count numbers) 2))

3

(dec (/ (count numbers) 2))

1

(nth numbers (dec (/ (count numbers) 2)))

2

median

(defn median [numbers]
  (let [n (count numbers)
        sorted-numbers (sort numbers)]
    (if (odd? n)
      (nth sorted-numbers (/ n 2))
      (let [mid1 (nth sorted-numbers (/ n 2))
            mid2 (nth sorted-numbers (dec (/ n 2)))]
        (float (/ (+ mid1 mid2) 2))))))

(median [1 2 3])

2

(median [1 2 3 4])

2.5

(median [2 1 3])

2

(median [2 1 4 3])

2.5

source: notebooks/median.clj