[SciPy-user] Designing Elliptic Filters

Adrian Lister alister at rocketmail.com
Sun Nov 19 14:29:11 CST 2006


I'm trying to get some elliptic filters for some crtitical band speech
processing to work in python and I seem to always get errors.  I've tried
changing my parameters and still nothing.  I can design Chebychev filters
and not error but elliptic just aren't working.  I have also designed the
filters in matlab and run them in python and that's fine.  The only thing
that I haven't been able to change is the computer that I'm running it on.
Suggestions / comments greatly appreciated

alister

n=5
rp=3
rs=80
wn=[.33,.66]

b,a=scipy.signal.ellip(n,rp,rs,wn)


Traceback (most recent call last):
  File "<pyshell#50>", line 1, in ?
    b,a=scipy.signal.ellip(5,3,80,[.33,.66])
  File "C:\Python24\lib\site-packages\scipy\signal\filter_design.py", line
516, in ellip
    return iirfilter(N, Wn, rs=rs, rp=rp, btype=btype, analog=analog,
output=output, ftype='elliptic')
  File "C:\Python24\lib\site-packages\scipy\signal\filter_design.py", line
444, in iirfilter
    z, p, k = typefunc(N, rp, rs)
  File "C:\Python24\lib\site-packages\scipy\signal\filter_design.py", line
1049, in ellipap
    disp=0)
  File "C:\Python24\lib\site-packages\scipy\optimize\optimize.py", line
140, in fmin
    N = len(x0)
TypeError: len() of unsized object





 
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