Here are two programs for your Maths share ware disc. I use them with an MSc class to look at signal processing. The nomenclicture used is from:-
Introductory digital signal processing with computer applications by Paul A. Lynn pub. John Wiley 1989 ISBN 0 471 91564
I have found this to be an excelent book.
LTIres - will plot the response of an LTI process for various input signals. Both the input signal and the LTI process can be defined using up to 3 recursive and 3 non recursive samples.
Pole_Zero - Will allow the placing of poles and zeros on a Z plane and will plot the resulting frequncy response. With attenuation shown in dBs and automatically scaled to a maximnum of -50dBs.
Both programs are written in BASIC and will return to the desktop. Some error checking is included but the Pole_Zero is by no means crash proofe.
I hope these programs will be of use to you.
All the best
Mike Cook - Department of Maths and Physics, Manchester Polytechnic.