# freqz: z-plane frequency response In signal: Signal Processing

 freqz R Documentation

## z-plane frequency response

### Description

Compute the z-plane frequency response of an ARMA model or IIR filter.

### Usage

``````## Default S3 method:
freqz(filt = 1, a = 1, n = 512, region = NULL, Fs = 2 * pi, ...)

## S3 method for class 'Arma'
freqz(filt, ...)

## S3 method for class 'Ma'
freqz(filt, ...)

## S3 method for class 'freqz'
print(x, ...)

## S3 method for class 'freqz'
plot(x, ...)

## Default S3 method:
freqz_plot(w, h, ...)

## S3 method for class 'freqz'
freqz_plot(w, ...)

``````

### Arguments

 `filt` for the default case, the moving-average coefficients of an ARMA model or filter. Generically, `filt` specifies an arbitrary model or filter operation. `a` the autoregressive (recursive) coefficients of an ARMA filter. `n` number of points at which to evaluate the frequency response. `region` `'half'` (the default) to evaluate around the upper half of the unit circle or `'whole'` to evaluate around the entire unit circle. `Fs` sampling frequency in Hz. If not specified, the frequencies are in radians. `w` for the default case, the array of frequencies. Generically, `w` specifies an object from which to plot a frequency response. `h` a complex array of frequency responses at the given frequencies. `x` object to be plotted. `...` for methods of `freqz`, arguments are passed to the default method. For `freqz_plot`, additional arguments are passed through to `plot`.

### Details

For fastest computation, `n` should factor into a small number of small primes.

When results of `freqz` are printed, `freqz_plot` will be called to display frequency plots of magnitude and phase. As with `lattice` plots, automatic printing does not work inside loops and function calls, so explicit calls to `print` or `plot` are needed there.

### Value

For `freqz` list of class `freqz` with items:

 `h` complex array of frequency responses at those frequencies. `f` array of frequencies.

### Author(s)

Original Octave version by John W. Eaton. Conversion to R by Tom Short.

### References

Octave Forge https://octave.sourceforge.io/

`filter`, `Arma`, `freqs`
``````b <- c(1, 0, -1)