def chebgrid3d(x, y, z, c):
c = chebval(x, c)<EOL>c = chebval(y, c)<EOL>c = chebval(z, c)<EOL>return c<EOL>
Evaluate a 3-D Chebyshev series on the Cartesian product of x, y, and z.

This function returns the values:

.. math:: p(a,b,c) = \\sum_{i,j,k} c_{i,j,k} * T_i(a) * T_j(b) * T_k(c)

where the points `(a, b, c)` consist of all triples formed by taking
`a` from `x`, `b` from `y`, and `c` from `z`. The resulting points form
a grid with `x` in the first dimension, `y` in the second, and `z` in
the third.

The parameters `x`, `y`, and `z` are converted to arrays only if they
are tuples or a lists, otherwise they are treated as a scalars. In
either case, either `x`, `y`, and `z` or their elements must support
multiplication and addition both with themselves and with the elements
of `c`.

If `c` has fewer than three dimensions, ones are implicitly appended to
its shape to make it 3-D. The shape of the result will be c.shape[3:] +
x.shape + y.shape + z.shape.

Parameters
----------
x, y, z : array_like, compatible objects
    The three dimensional series is evaluated at the points in the
    Cartesian product of `x`, `y`, and `z`.  If `x`,`y`, or `z` is a
    list or tuple, it is first converted to an ndarray, otherwise it is
    left unchanged and, if it isn't an ndarray, 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
--------
chebval, chebval2d, chebgrid2d, chebval3d

Notes
-----

.. versionadded::1.7.0