[SciPy-dev] RFR: #902 firwin upgrades

[Tom K.]

Thanks for the earlier review and discussion Chuck and others.  
Sorry it has taken so long to get back to this issue.  For now I have 
moved the PassBand class inside firwin to take it out of the 
filter_design module's local variables; let me know if you'd prefer
a different option for this class.  I've submitted a new patch
to the track issue, 
  http://projects.scipy.org/scipy/ticket/902

I think this patch is worth including for the following reasons:
  - it adds functionality to firwin that has been requested by scipy users,
in a way that is backwards compatible with the previous lowpass-only
functionality, that functionality being highpass, bandpass, bandstop, and
general multiband filters; also an option to *not* scale the filter is added
 - it adds a *test* for firwin where none existed before, testing different
filter lengths and options and making sure the frequency response is sane;
the test of course exercises not only the old functionality but the new as well.

Other questions about organization of signal (e.g. creating new modules for
fir filtering, or equiripple and window fir filter submodules) and
harmonization of different filter design routines (remez and window)
are not precluded and are largely orthogonal to incorporation of the new
functionality to this one small routine.

I see scipy as being an incredible resource and I would like to add this
tick mark to its feature list to compete with other commercial tools.
I would love to have scipy developed into a world class tool in every way
so that potential adopters are not able to cite the lack of some particular
feature as an excuse for sticking with a different commercial tool.