How to change the default x-axis unit in a Bode diagram to Hertz?
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Rad/s is nice for mechanical people, but I'm an EE, and I much prefer Hertz. It should be something simple, but I can't find it in the help.
2 Comments
dpb
on 22 Sep 2018
Don't believe there is a way in the base routine; it's built entirely around rad/timeunits per the system object.
You could write a wrapper routine to convert frequency units and update the plot labels.
Chris
on 4 Jan 2025
Actually you can, click on the plot tab from linearization manager, click plot properties, click units. Change to whatever units you need.
Accepted Answer
Star Strider
on 22 Sep 2018
It gives you that option, and the documentation specifically mentions that.
4 Comments
Star Strider
on 22 Sep 2018
Edited: Star Strider
on 22 Sep 2018
That is what I would do.
I defer to bodeplot because it allows some customization. I use and plot the bode outputs only if I want other options.
EDIT —
I add that this was my original recommendation!
More Answers (3)
Tjeerd Ickenroth
on 31 May 2023
Type 'ltiview' in your command window. The Linear System Analyzer will pop up. Click on: File --> Toolbox Preferences... --> Units --> Frequency: Hz
3 Comments
Tjeerd Ickenroth
on 31 May 2023
You need to change it once in the GUI and you always obtain bode plots in Hz. The setting remains even when you restart Matlab.
Dimitris Kalogiros
on 22 Sep 2018
clc;close all; clc
% test system
s=tf('s');
H=(s-1)/((s-3)*(s-2))
% bode
[mag,phase,wout] = bode(H);
%plot results, with frequency expressed at Hz
figure;
subplot(2,1,1);
semilogx(wout(:,1)/(2*pi), 20*log10(squeeze(mag)), '-b'); zoom on; grid on;
title('magnitude'); xlabel('Frequency (Hz)'); ylabel('Magnitude (dB)');
subplot(2,1,2);
semilogx(wout(:,1)/(2*pi), squeeze(phase), '-r'); zoom on; grid on;
title('Phase'); xlabel('Frequecy (Hz)'); ylabel('Phase (deg)');
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2 Comments
Meth Hai
on 15 Jul 2024
%%% G1 & and G2 is your TFs
[mag1, phase1, wout1] = bode(G1);
[mag2, phase2, wout2] = bode(G2);
% Convert angular frequency (rad/s) to frequency (Hz)
freq1 = wout1 / (2 * pi);
freq2 = wout2 / (2 * pi);
% Plot the magnitude response
figure;
subplot(2,1,1);
semilogx(freq1, 20*log10(squeeze(mag1)), '-b');
hold on;
semilogx(freq2, 20*log10(squeeze(mag2)), '-g');
grid on;
title('Magnitude');
xlabel('Frequency (Hz)');
ylabel('Magnitude (dB)');
legend('G1', 'G2');
%%%%%%%%%%%%
% Plot the phase response
subplot(2,1,2);
semilogx(freq1, squeeze(phase1), '-r');
hold on;
semilogx(freq2, squeeze(phase2), '-m');
grid on;
title('Phase');
xlabel('Frequency (Hz)');
ylabel('Phase (deg)');
legend('G1', 'G2');
Paul
on 5 Jan 2025
4 Comments
Paul
on 6 Jan 2025
Some things can be controlled programatically via settings. See Access and Modify Settings. Unfortunately, these don't cover the Control System Toolbox (why not?). As far as I know, the only way to deal with the CST is via ctrlpref, for which there is no programmatic interface (why not?), as far as I know. Those CST preferences are saved to disk somewhere somehow, so it might be possible copy them from one machine to another. You may want to open up a new question on this topic.
s = settings
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