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
> <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
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