How do I plot this?

How do I plot the magnitude of a transfer function H?

Answer 1

[Star Strider]

It depends on the Toolbox you’re using.

For a filter using the Signal Processing Toolbox, use the freqz (link) or freqs (link on the freqz page) functions.

For a control system using the Control System Toolbox, use the bode (link) function. Note that it is essentially impossible to change any of the plot characteristics using bode, so if you want to customise the plot, get the outputs from bode and plot them using the subplot function.

[Marc Adams]

Is it possible to use [mag,phase,wout] = bode(H) and then Y=squeeze(mag), then plotting Y to plot magnitude in terms of frequency?

[Star Strider]

Yes. That is the only way I know of to do it.

To replicate the bode plot result, this works:

figure
subplot(2,1,1)
semilogx(wout, 20*log10(squeeze(mag)), '-r', 'LineWidth',2)
grid
subplot(2,1,2)
semilogx(wout, squeeze(phase), '-r', 'LineWidth',2)
grid