freqs {gsignal}

Frequency response of analog filters

Description

Compute the s-plane frequency response of an IIR filter.

Usage

freqs(filt, ...)

## Default S3 method:
freqs(filt, a, w, plot = TRUE, ...)

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

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

## S3 method for class 'Sos'
freqs(filt, w, ...)

## S3 method for class 'Zpg'
freqs(filt, w, ...)

Arguments

filt

for the default case, moving average (MA) polynomial coefficients, specified as a numeric vector or matrix. In case of a matrix, then each row corresponds to an output of the system. The number of columns of b must be less than or equal to the length of a.

...

additional parameters (not used)

a

autoregressive (AR) polynomial coefficients, specified as a vector.

w

angular frequencies, specified as a positive real vector expressed in rad/second.

plot

logical. If TRUE (default), plots the magnitude and phase responses as a function of angular frequency, otherwise a vector of the frequency response is returned.

Details

The s-plane frequency response of the IIR filter B(s) / A(s) is computed as H = polyval(B, 1i * W) / polyval(A, 1i * W). If called with no output argument, a plot of magnitude and phase are displayed.

Value

Frequency response, returned as a complex vector.

Author(s)

Julius O. Smith III, [e-mail].
Conversion to R by Geert van Boxtel [e-mail]

Examples

b <- c(1, 2); a <- c(1, 1)
w <- seq(0, 4, length.out = 128)
freqs (b, a, w)