[Scipy-tickets] [SciPy] #1615: filter_design.py removing useful coefficients in normalize()
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Tue Apr 3 20:26:27 CDT 2012
#1615: filter_design.py removing useful coefficients in normalize()
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Reporter: waywardgeek | Owner: cdavid
Type: defect | Status: new
Priority: normal | Milestone: Unscheduled
Component: scipy.signal | Version: 0.10.0
Keywords: |
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Comment(by ldsalins):
I had the same issues trying to generate 6th order butterworth
coefficients on some data I was trying to filter. Adding atol=1e-14 as
the last argument to the allclose function in the section of the
filterdesign.py script described previously fixes this problem also. The
problem occurs because atol is set to 1e-8 by default. See below.
if allclose(outb[:,0], 0, rtol=1e-14, atol=1e-14):
warnings.warn("Badly conditioned filter coefficients (numerator):
the "
"results may be meaningless", BadCoefficients?)
while allclose(outb[:,0], 0, rtol=1e-14, atol=1e-14) and
(outb.shape[-1] > 1):
outb = outb[:,1:]
After I made the changes above, I compared scipy's output to Matlab's
output on the same data that I was previously having trouble generating
the coefficients for in Python and the output was identical. Python and
Scipy handle large datasets much better than Matlab. I hope this helps.
Thank you!
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Ticket URL: <http://projects.scipy.org/scipy/ticket/1615#comment:2>
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