[SciPy-User] butter() and filtfilt() - differences between MATLAB and scipy
Fri Jun 28 06:46:54 CDT 2013
On 28 June 2013 12:23, Roger Fearick <firstname.lastname@example.org> wrote:
> You're using Python 2.7: maybe 2/(256/2) = 0.
It's not this I'm afraid. I import division from __future__
>Tristan Strange a écrit :
>> In MATLAB [...] b comes out as a matrix containing :
>> 2.8109e-15 2.5298e-14 1.0119e-13 2.3612e-13 3.5418e-13
>> 2.3612e-13 1.0119e-13 2.5298e-14 2.8109e-15
>> When done in Python using scipy.signal's butter like so:
>> [...] the following warning is issued:
>> BadCoefficients: Badly conditioned filter coefficients (numerator): the
>> results may be meaningless "results may be meaningless",
> You should maybe worry about getting (in matlab) such values for b. All
> are pretty close to 0. This is what scipy implementation is warning you
> about ("Badly conditioned filter coefficients (numerator): the results
> may be meaningless"). Using this b vector may lead to output signals
> prone to numerical noise...
Ok, thanks. Apparently the MATLAB implementation functions as expected....
Any one else have any ideas?
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