Multiple Bode plots on same graph, how to plot phase ?

Hello,

My question has already been posted, but I'm having some trouble...

I'm trying to plot 2 bode plots on the same figure. One of the plots has a transfer function, the other not. So I use this command:

semilogx(x,y), hold on
bode(sys, 'r')

On this way I get 2 curves on the amplitude-plot, to this point all right. I'm looking to also add a second curve on the phase-plot. I tried using subplot(2,1,2), but it doesn't work...

Does anyone can tell me how to add this second phase-cure?

Thanks, Ata

[José-Luis]

Could you post an example of what you'd like and what you actually get? It doesn't work is not a very helpful description. Have you tried

 hold on

[ata]

This is wat I get for the moment : http://puu.sh/2XksL.png

I'd like to also plot a second blue curve in the phase-plot. This curve will be created from discrete data.

And yes I tried hold on after the subplot-command, but the graphic is totally replaced by the bode plot (i.e. the blue curve is not present).

Answer 1

[David Sanchez]

[mag_A phase_A] = bode(sys_A,W);
[mag_B phase_B] = bode(sys_B,W);
subplot(2,1,1)
semilogx(W,mag_A);hold on
semilogx(W,mag_B);hold off
subplot(2,1,2)
semilogx(W,phase_A);hold on
semilogx(W,phase_B);hold off

[ata]

Thanks for reply,

When trying this method I get an error :

 Error using ==> semilogx
 Data may not have more than 2 dimensions

I'm using an old version of Matlab (R2010b / 7.11.0), so it's maybe due to this fact...

[ata]

Oh right, I got it.

Here is the code I used:

[mag_A phase_A W] = bode(sys)
subplot(2,1,1)
semilogx(W,mag_A(:,:)); hold on
semilogx(x,y); hold off

and similar for the second subplot

[Patricia Darling]

Thank you! This works!