num.py 文件源码

def vander(points, deg):
    """N-dim Vandermonde matrix for data `points` and a polynomial of degree
    `deg`.

    Parameters
    ----------
    points : see polyfit()
    deg : int
        Degree of the poly (e.g. 3 for cubic).

    Returns
    -------
    vander : 2d array (npoints, (deg+1)**ndim)
    """
    powers = poly_powers(points.shape[1], deg)
    # low memory version, slower
    ##npoints = points.shape[0]
    ##vand = np.empty((npoints, (deg+1)**ndim), dtype=float)
    ##for ipoint in range(npoints):
    ##    vand[ipoint,:] = (points[ipoint]**powers).prod(axis=1)
    tmp = (points[...,None] ** np.swapaxes(powers, 0, 1)[None,...])
    return tmp.prod(axis=1)