Ariel Rokem wrote:
Hi Warren,
thanks for this example!
I am getting the following error:
Library/Frameworks/Python.framework/Versions/6.0.0/lib/python2.6/site-packages/scipy/signal/filter_design.py:224: BadCoefficients: Badly conditionned filter coefficients (numerator): the results may be meaningless "results may be meaningless", BadCoefficients)
For any attempt to filter a low-pass below 12 Hz in this example (so - I don't get the plot you got - instead I get a flat line on the bottom subplot). Do you (or anyone?) have any idea why that is?
Nils Wagner reported the same behavior a week or so ago, and I see the same behavior now ("BadCoefficients" and a flat line in the last plot). Try lowering the order of the Butterworth filter to order=6. Warren
Cheers,
Ariel
On Wed, Feb 24, 2010 at 7:51 AM, Warren Weckesser <warren.weckesser@enthought.com <mailto:warren.weckesser@enthought.com>> wrote:
Nils Wagner wrote: > Hi all, > > I have two questions concerning signal processing > > I have used scipy.stats.signaltonoise to compute the > signal-to-noise ratio. > The value is 0.0447. > How can I judge it ? > > How can I filter out high frequencies using scipy ? >
I posted an example low-pass filtering using 'butter' and 'lfilter' from scipy.signal here:
http://mail.scipy.org/pipermail/scipy-user/2010-January/024032.html
Warren
> How can I eliminate noise from the signal ? > > Nils > _______________________________________________ > SciPy-User mailing list > SciPy-User@scipy.org <mailto:SciPy-User@scipy.org> > http://mail.scipy.org/mailman/listinfo/scipy-user >
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-- Ariel Rokem Helen Wills Neuroscience Institute University of California, Berkeley http://argentum.ucbso.berkeley.edu/ariel ------------------------------------------------------------------------
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