signal (version 0.5)

freqz: s-plane frequency response

Description

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

Usage

## S3 method for class 'default':
freqz(filt = 1, a = 1, n = 512, region = NULL, Fs = 2 * pi, \ldots)

## S3 method for class 'Arma':
freqz(filt, \ldots)

## S3 method for class 'Ma':
freqz(filt, \ldots)

## S3 method for class 'freqz':
print(x, \ldots)

## S3 method for class 'freqz':
plot(x, \ldots)

## S3 method for class 'default':
freqz_plot(w, h, \ldots) 

## S3 method for class 'freqz':
freqz_plot(w, \ldots)

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.

Value

• For freqz list of class freqz with items:
• h
  array of frequencies.
• f
  complex array of frequency responses at those frequencies.

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.

References

Octave Forge http://octave.sf.net

See Also

filter, Arma, freqs

Examples

b = c(1,0,-1)
a = c(1,0,0,0,0.25)
freqz(b, a)