MATLAB: Can I zoom an area in Bode magnitude diagram

bode magnitudezoom

Hi everyone; I have a bode magnitude diagram but i need to zoom the first peak point on the same bode magnitude diagram. Thanks in advance

Best Answer

The bode function has some restrictions. However you can use the GUI zoom, pan, data cursor, and other functions as you would in any other plot window. Click the magnifying glass with the + sign to zoom in, and the one with the - sign to zoom out. All the other plot window GUI functions work with bode as well.

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MATLAB: Change marker width in bode plot

The bode function doesn’t accept many options with respect to its plots. The easiest way to do what you want is to request at least the first three outputs of the bode function, and then plot them using subplot and plot. The plots are the same as any other plot object:

[mag,phase,wout] = bode(sys);
subplot(2,1,1)
plot(wout, mag)
subplot*2,1,2)
plot(wout, phase)

Use ‘20*log10(mag)’ to plot the magnitude in decibels, and semilogx instead of plot to make the plot look like those bode produces on its own:

[mag,phase,wout] = bode(sys);
subplot(2,1,1)
semilogx(wout, 20*log10(mag))
subplot*2,1,2)
semilogx(wout, phase)

MATLAB: How to find bode plot,phase magnitude plot and template in control system

This works, although you will have to plot 171 figures to see each of them with any detail. (You would have to have a very large monitor to see them all as the bode function plots them, since it plots an array of (2x171) subplots in one figure.)

The Code —

[mag,phs,wout] = bode(sys);
Magnitude = squeeze(mag);
Phase = squeeze(phs);
figure(1)
subplot(2,1,1)
plot(wout,20*log10(Magnitude(1,:)))
title('Magnitude (dB)')
grid
subplot(2,1,2)
plot(wout,Phase(1,:))
title('Phase (°)')
grid

The ‘template’ is a Simulink function you will have to do yourself, since you have to specify how you want it.

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MATLAB: Change marker width in bode plot

MATLAB: How to find bode plot,phase magnitude plot and template in control system

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