estimator.py 文件源码

def dowd(X):
    """
    Return the Dowd Variogram of the given sample X.
    X has to be an even-length array of point pairs like: x1, x1+h, x2, x2+h ...., xn, xn + h.
    If X.ndim > 1, dowd will be called recursively and a list of Cressie-Hawkins Variances is returned.

    Dowd, P. A., (1984): The variogram and kriging: Robust and resistant estimators, in Geostatistics for Natural
        Resources Characterization. Edited by G. Verly et al., pp. 91 - 106, D. Reidel, Dordrecht.

    :param X:
    :return:
    """
    _X = np.array(X)

    if any([isinstance(_, list) or isinstance(_, np.ndarray) for _ in _X]):
        return np.array([dowd(_) for _ in _X])

    # check even
    if len(_X) % 2 > 0:
        raise ValueError('The sample does not have an even length: {}'.format(_X))

    # calculate
    term1 = np.nanmedian([np.abs(_X[i] - _X[i + 1]) for i in np.arange(0, len(_X) - 1, 2)])
    return 0.5 * (2.198 * np.power(term1, 2))