<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def hfd(X, Kmax):
 """ Compute Hjorth Fractal Dimension of a time series X, kmax is an HFD parameter """

    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]