exponential-smooth.clj

(defn- exponential-smooth-recur
  [current v factor]
  (if (empty? v)
    (rest current)
    (letfn [(smooth
      [y m]
      (+ (* (- 1 factor) m) (* factor y)))]
      (recur (conj current (smooth (first v) (last current))) (rest v) factor))))

(defn exponential-smooth
  [v factor]
  (exponential-smooth-recur [(first v)] v factor))

(println (exponential-smooth impressions 0.9))