How do I get a magnitude respons with frequency at the x-axis?

When I use the function freqz() I'll get a response with normalized frequency at the x-axis. Is there a way to get the freqency instead or optionally calculate it by hand?

Answer 1

[Star Strider]

Yes!

Supply the sampling frequency (here ‘Fs’) as an argument to freqz to get the plot in terms of actual frequency (from 0 Hz to the Nyquist frequency), where ‘NFFT’ is the length of the Fourier transform you want to use (a good choice being 2^16):

freqz(sos, NFFT, Fs)

or:

freqz(b, a, NFFT, Fs)

or others, depending on how you implemented your filter.

[Joakim Hansen]

Thank you!

[Star Strider]

As always, my pleasure!