code: def hfd(X, Kmax):
      
      L = []
      x = []
      N = len(X)
      for k in range(1, Kmax):
          Lk = []
          for m in range(0, k):
              Lmk = 0
              for i in range(1, int(numpy.floor((N - m) / k))):
                  Lmk += abs(X[m + i * k] - X[m + i * k - k])
              Lmk = Lmk * (N - 1) / numpy.floor((N - m) / float(k)) / k
              Lk.append(Lmk)
          L.append(numpy.log(numpy.mean(Lk)))
          x.append([numpy.log(float(1) / k), 1])
  
      (p, r1, r2, s) = numpy.linalg.lstsq(x, L)
      return p[0]
docs: Compute Hjorth Fractal Dimension of a time series X, kmax
       is an HFD parameter