Should I use 1-D digital filtering or lowpass filter ?

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Hi All
which of the two is better for random signals ( i have 6 signals in 6 degrees of freedom : should I filter them together with the same values of filter ?)
and what does this mean :
lowpass uses a minimum-order filter with a stopband attenuation of 60 dB
It's also not clear how should I calculate wpass for a given random signal !!
with normalized passband frequency wpass in units of π rad/sample
what should I read from my signal to calculate the wpass?

Accepted Answer

Star Strider
Star Strider on 6 Apr 2020
Edited: Star Strider on 6 Apr 2020
Yes. Also be certain that the signals have uniform sampling intervals. If they do not, use the resample function to force them to be regularly-sampled.
The lowpass function uses the shortest (i.e. most efficient) filter that will give the appropriate results, and the stopband is 60 dB lower than the passband, or 1/1000 the passband amplitude.
EDIT — (6 Apr 2020 at 20:49)
The ‘wpass’ argument is the passband frequency in units of radians/sample, with π being defined as equivalent to the Nyquist frequency (one-half the sampling frequency).
If you use the ‘fs’ argument as well, you can instead designate ‘fpass’ in the same frequency units as ‘fs’ (for example, Hz). The normalisation will be done automatically.
  4 Comments
farzad
farzad on 6 Apr 2020
thank you very much, in this case of 1024 Hz, what will be wpass ? how do I calculate it ?
Star Strider
Star Strider on 7 Apr 2020
As always, my pleasure!
Please see my previous Comment. I provided code for exactly that for a sampling frequency of 1024 Hz and a passband of 0 to 256 Hz.

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