how many terms uses the function hypergeom

If we use the matlab build in function

hypergeom(N,D,z)

which is a infitite sum

hypergeom(N,D,z) = sum(k=0:inf, (C(N,k)/C(D,k))*z^k/k!)

How many terms are used? I.e. what is

inf

Thank you very much for any suggestions!

Best,

Rafael

[Walter Roberson]

hypergeom is executed inside the symbolic engine. The symbolic engine uses as many terms as it needs to in order to meet the tolerance that is in effect at the time.

[Rafael Schwarzenegger]

Thank you very much. Is there an expression for the error. What is the tolerance set to in the symbolic engine?

[Walter Roberson]

At the MATLAB command prompt give the command

mupad

MATLAB will whine and try to convince you to use LiveScript instead. Do not let it use LiveScript: tell it to go ahead and open a MuPAD notebook.

Once the MuPAD notebook has opened, and you are at the [ prompt, type in the command

expose(hypergeom)

You will see that there are a couple of hundred lines of code, and that there are dozens of special cases that are handled, including some cases where the calculations is built up recursively. We cannot really talk about the error analysis unless we know which case is being invoked.

[Rafael Schwarzenegger]

Thank you very much. It answers my question well.