rray, it is treated as a
    scalar.
c : array_like
    Array of coefficients ordered so that the coefficients for terms of
    degree i,j are contained in ``c[i,j]``. If `c` has dimension
    greater than two the remaining indices enumerate multiple sets of
    coefficients.

Returns
-------
values : ndarray, compatible object
    The values of the two dimensional polynomial at points in the Cartesian
    product of `x` and `y`.

See Also
--------
polyval, polyval2d, polygrid2d, polyval3d

Examples
--------
>>> from numpy.polynomial import polynomial as P
>>> c = ((1, 2, 3), (4, 5, 6), (7, 8, 9))
>>> P.polygrid3d([0, 1], [0, 1], [0, 1], c)
array([[ 1., 13.],
       [ 6., 51.]])

r