def cov_pow(h, w=1.0, r=1.0, s=1.0):
    """
    1D-power covariance model (with sill=1 and range=1):

    :param h:   (1-dimensional array or float): lag(s)
    :param w:   (float >0): weight (sill)
    :param r:   (float >0): range
    :param s:   (float btw 0 and 2): power
    :return:    (1-dimensional array or float) evaluation of the model at h
    """
    return (w * (1. - (h/r)**s))