[albertcardona]

Very nice, thanks for sharing! For my own purposes I implemented the function in clojure, which I find more readable. Destructuring and literal vectors are great assets of clojure. Autopromotion to avoid overflow (as in common lisp) is also great.

  (defn mean-variance [data]
    (let [square (fn [x] (* x x))
          [n xs x2s] (reduce (fn [accum xi]
                               [(inc (accum 0))
                                (+ (accum 1) xi)
                                (+ (accum 2) (square xi))])
                             [0 0 0]
                             data)
          mu (/ xs n)]
      [mu (- (/ x2s n) (square mu))]))