Graphical DSP filter design?

[Mark Knecht]

Hi,
   I'm interested in doing a little bit of digital filter design.
Looking around for Open Source tools I've just discovered Scilab and
I'm wondering if it's well suited to this sort of study? Mainly I'd
like to be able to input block level diagrams such as the one on this
page:

http://en.wikipedia.org/wiki/Finite_impulse_response

and then set parameters and see amplitude and phase response.

   Scilab looks like it is probably capable of this sort of work but
other than the very long (3400 pages?) user's manual I haven't found
any examples of doing this sort of thing as of yet.

   Thanks in advance.

Cheers,
Mark