freqs function

Frequency response of analog filters

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

freqs(filt, ...)

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

## 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, ...)

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

## S3 method for class 'freqs'
summary(object, ...)

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

freqs_plot(x, ...)

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

Returns

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

• h: complex array of frequency responses at frequencies f.
• w: array of frequencies.

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)

Author(s)

Julius O. Smith III, jos@ccrma.stanford.edu .

Conversion to R by Geert van Boxtel gjmvanboxtel@gmail.com