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

## Description

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

## Usage

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20``` ```## 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`

## Examples

 ```1 2 3``` ```b <- c(1, 0, -1) a <- c(1, 0, 0, 0, 0.25) freqz(b, a) ```

### Example output

```Attaching package: 'signal'

The following objects are masked from 'package:stats':

filter, poly
```

signal documentation built on May 25, 2021, 9:06 a.m.