On Mon, Apr 21, 2008 at 12:58 PM, Richard Hennessy <rvh2007 at comcast.net>
wrote:
> I wanted something like this so thanks. The only thing is the degree of
> the polynomials. I used the quadratic case as an example but really the
> reason I asked about this is that I have a power series in x and y and I
> needed to keep a lot of terms for accuracy. In one case to get sufficient
> accuracy I used 500 terms.
>
For speed of calculation of your f(x,y), you should surely be using the
canonical rational expression (CRE) representation, either as general
rational functions (rat) or as truncated power series (taylor). Your
calculations will be radically faster because intermediate results will be
kept in canonical form.
Try f(rat(x),rat(y)), for example.
After you are done with the calculation, you can choose to display in a
variety of ways. The standard way of displaying CREs is as a polynomial of
polynomials, e.g. (y^2+1)*x^2 + (y^3+y)*x + y - 3, but using the flags
psexpand and ratexpand you can display other forms.
-s