[SciPy-user] filtering without phase shift

Jonathan Merritt j.merritt@pgrad.unimelb.edu...
Mon Jul 23 22:43:10 CDT 2007

Hi Ryan,

Ryan Krauss wrote:
> Is there a way to get magtitude
> attenuation without phase lag that is easy to implement and accepted
> as good practice among signal processing experts?

This is a very common problem in Biomechanics, where we often want to 
take the second derivative of noisy signals.

Matlab has a filtfilt() function for applying a zero phase delay filter, 
and I have seen a SciPy implementation here:

I can't comment on whether this implementation is "good".  I'd like to 
hear from any signal processing experts too. :-)

Jonathan Merritt.

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