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Phase response of digital filter

`[phi,w] = phasez(b,a,n)[phi,w] = phasez(sos,n)[phi,w] = phasez(d,n)[phi,w] = phasez(...,n,`

`[phi,w] = phasez(b,a,n)` returns
the `n`-point unwrapped phase response vector, `phi`,
in radians and the frequency vector, `w`, in radians/sample
for the filter coefficients specified in `b` and `a`.
The values of the frequency vector, `w`, range from
0 to *π*. If `n` is omitted,
the length of the phase response vector defaults to 512.

`[phi,w] = phasez(sos,n)` returns the unwrapped
phase response for the second order sections matrix, `sos`. `sos` is
a *K*-by-6 matrix, where the number of sections, *K*,
must be greater than or equal to 2. If the number of sections is less
than 2, `phasez` considers the input to be the
numerator vector, `b`. Each row of `sos` corresponds
to the coefficients of a second-order (biquad) filter. The *i*th
row of the `sos` matrix corresponds to `[bi(1)
bi(2) bi(3) ai(1) ai(2) ai(3)]`.

`[phi,w] = phasez(d,n)` returns the unwrapped
phase response for the digital filter, `d`. Use `designfilt` to generate `d` based
on frequency-response specifications.

`[phi,w] = phasez(...,n, 'whole')` returns
frequency and unwrapped phase response vectors evaluated at

`phi = phasez(...,w)` returns
the unwrapped phase response in radians at frequencies specified in `w` (radians/sample).
The frequencies are normally between 0 and *π*.
The vector `w` must have at least two elements.

`[phi,f] = phasez(...,n,fs)` return
the unwrapped phase vector `phi` in radians and the
frequency vector in hertz. The frequency vector ranges from 0 to the
Nyquist frequency, `fs/2`. If the `'whole'` option
is used, the frequency vector ranges from 0 to the sampling frequency.

`phi = phasez(...f,fs)` return
the phase response in radians at the frequencies specified in the
vector `f` (in hertz) using the sampling frequency `fs` (in
hertz). The vector `f` must have at least two elements.

`[phi,w,s] = phasez(...)` return
plotting information, where `s` is a structure array
with fields you can change to display different frequency response
plots.

`phasez(...)` with no output
arguments plots the phase response of the filter. If you input the
filter coefficients or second order sections matrix, the current figure
window is used. If you input a `digitalFilter`, the step response is displayed in `fvtool`.

`designfilt` | `digitalFilter` | `freqz` | `fvtool` | `grpdelay` | `phasedelay`

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