The DerivativeRepresentation(S, x) calling sequence returns a series equal to S written in terms of the family of polynomials produced by differentiating the S polynomials with respect to x.

The DerivativeRepresentation(S, x1,.., xn) and DerivativeRepresentation(S, [x1,.., xn]) calling sequences are equivalent to the recursive calling sequence DerivativeRepresentation(...DerivativeRepresentation(S, x1),..., xn).

The partial differential representation can be used for continuous hypergeometric polynomials with a degree 2 sigma polynomial. The partial differential representation (with respect to the root xi for the polynomials poly(n, x) depending on x in the series S) is obtained by using the DerivativeRepresentation(S, x, root=val) calling sequence. If val is not a root of the sigma associated with poly(n, x), an error message is returned. The DerivativeRepresentation(S, x1,.., xn, root=val) and DerivativeRepresentation(S, [x1,.., xn], root=val) calling sequences assume that all polynomials depending on x1,.., xn share the common root val. Otherwise, an error is returned.

Error, (in OrthogonalSeries:-DerivativeRepresentation) -2 is not a root of x^2-1