numpy.polynomial.legendre.legvander3d¶

numpy.polynomial.legendre.
legvander3d
(x, y, z, deg)[source]¶ PseudoVandermonde matrix of given degrees.
Returns the pseudoVandermonde matrix of degrees deg and sample points (x, y, z). If l, m, n are the given degrees in x, y, z, then The pseudoVandermonde matrix is defined by
where 0 <= i <= l, 0 <= j <= m, and 0 <= j <= n. The leading indices of V index the points (x, y, z) and the last index encodes the degrees of the Legendre polynomials.
If
V = legvander3d(x, y, z, [xdeg, ydeg, zdeg])
, then the columns of V correspond to the elements of a 3D coefficient array c of shape (xdeg + 1, ydeg + 1, zdeg + 1) in the orderand
np.dot(V, c.flat)
andlegval3d(x, y, z, c)
will be the same up to roundoff. This equivalence is useful both for least squares fitting and for the evaluation of a large number of 3D Legendre series of the same degrees and sample points.Parameters:  x, y, z : array_like
Arrays of point coordinates, all of the same shape. The dtypes will be converted to either float64 or complex128 depending on whether any of the elements are complex. Scalars are converted to 1D arrays.
 deg : list of ints
List of maximum degrees of the form [x_deg, y_deg, z_deg].
Returns:  vander3d : ndarray
The shape of the returned matrix is
x.shape + (order,)
, where . The dtype will be the same as the converted x, y, and z.
Notes
New in version 1.7.0.