Error plotting bode diagram of a transfer function inside a matrix

I am trying to plot bode diagram of an element inside a matrix. The transfer function is alright if i plot G11 which is first row first column matrix. But the bode plot gives error. Is there a different way to plot such bode diagram ? My code is below.

syms s
    G11=s-1;G12=s;
    G21=-6;G22=s-2;
    den=1.25*(s+1).*(s+2);
    G=[G11, G12;G21, G22]/den;
   
   G1=G(1,1);
    G2=G(1,2);
    G3=G(2,1);
    G4=G(2,2);  
  bode(G1)

I even tried G11 by removing all G1...G4. But still doesnt work. Please guide.

[Star Strider]

Shah Fahad’s Answer moved here —

The error is:

Error using bode (line 83)

Not enough input arguments.

[ahmed solyman]

Regarding MATLAB coding in particular using the bode(sys) code to get the bode diagram. When the numerator equals just a number like (10) without (S), there is an error in computing the bode magnitude because computing it as a 20log(k) “the rule” is not true in MATLAB. Because MATLAB takes into consideration it as log “ln”, not log10.

Please could you tell me how I can solve this issue?

Answer 1

[Star Strider]

That is not the error.

The error is that you are using the Symbolic Math Toolbox when you need to be using the Control System Toolbox.

Try this:

s = tf('s');
G11=s-1;G12=s;
G21=-6;G22=s-2;
den=1.25*(s+1).*(s+2);
G=[G11, G12;G21, G22]/den;

G1=G(1,1);
G2=G(1,2);
G3=G(2,1);
G4=G(2,2);
bode(G1)

[Shah Fahad]

Dear @strider,

Thank you so much for your response. My code is working now.

Thank you.

[Star Strider]

As always, my pleasure!