[SciPy-User] Signal processing 101: creating and applying a bandpass filter

[Rob Newman]

Dear SciPy gurus,

I have a list of values that I wish to apply a bandpass filter to. Looking at the docs (http://docs.scipy.org/doc/scipy/reference/signal.html), I can see how to design a filter (http://docs.scipy.org/doc/scipy/reference/generated/scipy.signal.butter.html), but I don't see any examples of using your custom designed filter in practice with lists or arrays. Are there any online resources that show step-by-step how to build a filter and apply to a list of values?

For example, here is a Python list:

[1.2711705420245039e-05,
 -2.7804792241996774e-05,
 3.6106973477276575e-05,
 -1.3862942711545279e-05,
 -4.5308686748537353e-06,
 3.9977066695205231e-06,
 -1.4130285261627493e-06,
 -3.992578793440835e-07,
<snip>
 8.7310453451921392e-07,
 -1.2458364494266352e-06,
 1.972281982220939e-06,
 -2.5749765923225825e-06,
 3.4605357526068371e-06,
 -7.4952550588555781e-06]

It is 512 in length.

I want to apply a Butterworth-style filter to this data, using a similar format of the string below (or translated to how the SciPy bandpass filtering works):

0.02_5_0.10_5

where a 0.02Hz to 0.10Hz bandpass filter is applied, with the 5's representing the poles of the filters.

I hope this makes sense. Please let me know if I need to clarify in any way.

Thanks in advance,
- Rob
________________________________________________________

Rob Newman
Institute of Geophysics and Planetary Physics
Scripps Institution of Oceanography
University of California, San Diego
9500 Gilman Drive, La Jolla, CA 92093-0225, USA