gistfile1.txt

;; http://www.johndcook.com/standard_deviation.html
(defn online-var
  [x]
  (loop [xs x
         k 1
         m (first x)
         s 0]
    (let [x (first xs)
          mk (+ m (float (/ (- x m) k)))]
      (if (empty? (rest xs))
        (/ s (- k 1))
        (recur (rest xs)
               (inc k)
               mk
               (+ s (* (- x m) (- x mk))))))))