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I have a signal that was recorded with around 300 samples in a second. Now I want to run a low pass and a high pass butterworth filter over it. The frequency for the high pass filter is around 0.05 Hz and the one for the low pass around 5 Hz.

But how can I decide which order my butterworth filters should have? Is there any formula?

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    $\begingroup$ To answer this properly you will first need to provide a complete filter specification: width of transition band, maximum passband ripple, minimum stopband rejection, etc. $\endgroup$ – Paul R May 1 '13 at 9:40
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    $\begingroup$ Are you sure you want a Butterworth filter? If your filter doesn't need to be maximally flat you might be better off with a Cauer (elliptic) filter. $\endgroup$ – Matt L. May 1 '13 at 10:00
  • $\begingroup$ Do you mean that the high-pass filter has a cutoff frequency of 0.05 Hz and the low-pass filter has a cutoff frequency of 5 Hz? If so, what are the pass band frequencies? $\endgroup$ – Jim Clay May 1 '13 at 13:41
  • $\begingroup$ It seems like you've been asked a series of clarification questions that you haven't responded to. I'm afraid I'm going to have to close this as "not sure what you're asking". Do you think you can provide some clarification? $\endgroup$ – Phonon Oct 30 '13 at 1:40

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