gsignal (version 0.3-7)

freqs: Frequency response of analog filters

Description

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

Usage

freqs(filt, ...)
# S3 method for default
freqs(filt, a, w, ...)
# S3 method for Arma
freqs(filt, w, ...)
# S3 method for Ma
freqs(filt, w, ...)
# S3 method for Sos
freqs(filt, w, ...)
# S3 method for Zpg
freqs(filt, w, ...)
# S3 method for freqs
print(x, ...)
# S3 method for freqs
summary(object, ...)
# S3 method for summary.freqs
print(x, ...)
freqs_plot(x, ...)

Value

For freqs, a list of class 'freqs' with items:

h

complex array of frequency responses at frequencies f.

w

array of frequencies.

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.

...

for methods of freqs, arguments are passed to the default method. For freqs_plot, additional arguments are passed through to plot.

a

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

w

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

x

object to be printed or plotted.

object

object of class "freqs" for summary

Author

Julius O. Smith III, .
Conversion to R by Geert van Boxtel

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.

Examples

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