Exponential smooth for incanter

exp_smooth.clj

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;; SMOOTHING
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(defn exponential-smooth
"
    Smooths a sequence with an exponentially decreasing weight.

    Arguments:
      x -- a sequence of numbers
      f -- the smoothing factor (between 0 and 1). close to 0 will produce
           a stronger smoothing effect less responsive to recent values. closer
           to 1 will have less of an effect and give greater weight to recent
           values.

    Examples:
        (exponential-smooth (range 1 500) 0.9)

    References:
        http://en.wikipedia.org/wiki/Smoothing
        http://en.wikipedia.org/wiki/Exponential_smoothing
"
 [x f]
 (letfn [
   (smooth
     [alpha st xt]
     (conj st
       (+
         (* alpha xt)
         (* (- 1 alpha) (last st)))))]
   (reduce (partial smooth f) [(first x)] (rest x))))