utility.py 文件源码

def has_constant(x):
    """
    Parameters
    ----------
    x: ndarray
        Array to be checked for a constant (n,k)

    Returns
    -------
    const : bool
        Flag indicating whether x contains a constant or has column span with
        a constant
    loc : int
        Column location of constant
    """
    if np.any(np.all(x == 1, axis=0)):
        loc = np.argwhere(np.all(x == 1, axis=0))
        return True, int(loc)

    if np.any((np.ptp(x, axis=0) == 0) & ~np.all(x == 0, axis=0)):
        loc = np.any((np.ptp(x, axis=0) == 0) & ~np.all(x == 0, axis=0))
        loc = np.argwhere(loc)
        return True, int(loc)

    n = x.shape[0]
    aug_rank = matrix_rank(np.c_[np.ones((n, 1)), x])
    rank = matrix_rank(x)
    has_const = bool(aug_rank == rank)
    loc = None
    if has_const:
        out = np.linalg.lstsq(x, np.ones((n, 1)))
        beta = out[0].ravel()
        loc = np.argmax(np.abs(beta) * x.var(0))
    return has_const, loc