Moving avarage

moving-avarage.clj

(defn- slide [window x]
  (-> window (subvec 1) (conj x)))

(defn- windows [n xs]
  (let [first-window (vec (take n xs))
        the-rest (drop n xs)]
    (when (and (< 0 n) (= n (count first-window)))
      (reductions slide first-window the-rest))))

(defn- avarage [xs]
  (/ (apply + xs) (count xs)))

(defn moving-avarage [n xs]
  (->> xs (windows n) (map avarage)))

(moving-avarage 1 []) ; => ()
(moving-avarage -1 [1 2 3 4]) ; => ()
(moving-avarage 0 [1 2 3 4]) ; => ()
(moving-avarage 1 [1 2 3 4]) ; => (1 2 3 4)
(moving-avarage 2 [1 2 3 4]) ; => (3/2 5/2 7/2)
(moving-avarage 3 [1 2 3 4]) ; => (2 3)
(moving-avarage 4 [1 2 3 4]) ; => (5/2)
(moving-avarage 5 [1 2 3 4]) ; => ()
(nth (moving-avarage 3 (range)) 1000000) ; => 1000001