Why does the Bode function behaves differently in a subplot?

Hi,

I want to run a script several times in a row, where every run new lines are plotted in a Bode diagram. This does not work when I use subplots, see the simple example below. Both lines are plotted this way, but the first line disappears when the 2 lines are uncommented and the example is rerun. So how can I plot these 2 lines in 1 Bode subplot? Thank you in advance!

Best regards, Laszlo

H = tf([1],[100]);

figure(100)

% subplot(2,1,1)

hold on

bodemag(H)

grid on

defcol

H = tf([1],[1 0 0]);

figure(100)

% subplot(2,1,1)

hold on

bodemag(H)

grid on

defcol

Answer 1

[Arkadiy Turevskiy]

This works:

H = tf([1],[100]);
figure(100)
subplot(2,1,1);
[mag,ph,wout]=bode(H);
semilogx(wout,20*log10(squeeze(mag)));
grid on
xlabel('Frequency (rad/sec)');
ylabel('Magnitude (dB)');
title('Bode Diagram');
hold on;
H = tf([1],[1 1 0]);
figure(100)
subplot(2,1,1)
[mag,ph,wout]=bode(H);
semilogx(wout,20*log10(squeeze(mag)));

[laszlo]

That works great. Thanks a lot!

Answer 2

[Thorsten]

This litte script works for me; maybe something unexpected is going on in your bodemag function?

function plotdata(s)

figure(100)
subplot(2,1,1)
hold on
plot(1:10, s*rand(1,10), 'k')
grid on

figure(100)
subplot(2,1,1)
hold on
plot(1:10, s*rand(1,10), 'r')
grid on

[laszlo]

Thanks Thorsten for your answer. I agree, several lines can be plotted when using the 'plot' command in subplots. Unfortunately, the same approach does not work for Bode. In my script I didn't change the bodeoptions, I just use the default settings. I have no clue why Bode has problems while plot works..

[Thorsten]

I don't have the System Identification TB, so I have to ask if this works for you:

 bodemag(gca, H)

[laszlo]

Too bad, that does not solve the problem.