Signal Processing Toolbox

freqzplot

Plot frequency response data.

Syntax

freqzplot(h,w)
freqzplot(h,w,s)

Description

freqzplot(h,w) plots the frequency response data contained in h at the frequencies specified in the vector w, where h can be either a vector or a matrix. w must be a vector whose length is the number of rows in h. The data in h is plotted versus frequency w on two plots:

• The magnitude of h is plotted in dB.
• The phase of h is plotted in degrees.

The units for frequency on the plots are in radians per sample. If h is a matrix, the frequency responses of each column of h is plotted.

freqzplot(h,w,s) specifies a structure of plotting options, s, with the following fields:

• s.xunits - a string specifying the frequency axis units. The contents of s.xunits can be one of the following:
• 'rad/sample' (default)
• 'Hz'
• 'kHz'
• 'MHz'
• 'GHz'
• A user-specified string
• s.yunits - a string specifying the vertical axis units. The contents of s.yunits can be one of the following:
• 'dB' (default)
• 'linear'
• 'squared'
• s.plot - a string specifying the type of plot to produce. The contents of s.plot can be one of the following:
• 'both' (default)
• 'mag'
• 'phase'

Note that the s structure can be obtained as an output of freqz.

Examples

nfft = 512; Fs = 44.1;            % Fs is in kHz.
[b1,a1]  = cheby1(5,0.4,0.5);
[b2,a2]  = cheby1(5,0.5,0.5);
[h1,f,s] = freqz(b1,a1,nfft,Fs);
h2       = freqz(b2,a2,nfft,Fs);% Use the same nfft and Fs.
h = [h1 h2];
s.plot   = 'mag';        % Plot the magnitude only.
s.xunits = 'khz';        % Label the frequency units correctly.
s.yunits = 'squared';    % Plot the magnitude squared.
freqzplot(h,f,s);        % Compare the two Chebyshev filters.

See Also

freqz	Compute and plot the frequency response of a filter.
grpdelay	Compute the average filter delay.
psdplot	Plot power spectral density (PSD) data.

freqz

gauspuls