Matlab higher order Bode error

Hey,

I searched the site for this problem, people asked same questions, however I couldn't find any working answer for my problem.

The problem is, when I try to draw a Bode plot of second or higher order such as,

>> G=tf([1], [1 1 1]);

>> bode(G)

I get an error message saying

Error using  + 
Matrix dimensions must agree.

Error in freqgrid>psum (line 387)
p = [zeros(1,l2-l1) p1] + [zeros(1,l1-l2)
p2];

Error in freqgrid>LocalAddPhaseExtrema
(line 349)
rhs1 =
psum(conv(d1,d2),2*[psum(conv(polyder(d2),d1),-conv(polyder(d1),d2))
0]);

Error in freqgrid (line 138)
   w = LocalAddPhaseExtrema(w,z{1},p{1});

Error in ltipack.ltidata/freqresp (line
45)
   w = freqgrid(z,p,Ts,Grade,Focus);

Error in resppack.ltisource/magphaseresp
(line 34)
         [mag,phase,w,FocusInfo] =
         freqresp(SysData(ct),grade,wspec,true);

Error in wavepack.waveform/draw (line 25)
   feval(this.DataFcn{:});

Error in wrfc.plot/draw (line 17)
      draw(wf)

Error in
wrfc.plot/init_listeners>LocalRefreshPlot
(line 79)
   draw(this)

Warning: Error occurred while evaluating
listener callback. 
> In DynamicSystem/bodeplot (line 140)
  In DynamicSystem/bode (line 95)

"Bode" command works for first order transfer functions though.

Can you explain what is the problem ?

Thanks in advance

[Star Strider]

Your code:

G=tf([1], [1 1 1]);
bode(G)

runs without error for me in R2016b, and produces the appropriate plot.

[ANIL ALAN]

Hi Star Strider,

Actually that is the main problem, because it is a simple command and should work, but it doesn't ! I tried this on R2015a and R2015b on same computer but kept giving the error. When I used a friend's PC it worked like your try. Is something wrong with any of PC settings ?

Anıl

[Star Strider]

Hi Anil,

It’s time for you to Contact Support.

Answer 1

[Joshua Long]

This error can occur if the "draw.m" function used to draw the Bode plot is corrupted or if a defined function is getting higher priority over the default system defined function.

To resolve this issue please execute the following commands in you MATLAB command prompt and restart MATLAB:

 >> rehash toolboxcache
 >> restoredefaultpath
 >> savepath

[ANIL ALAN]

Hi,

Thank you for the answer.

When I run the command

restoredefaultpath

it gives the warning

Warning: Duplicate directory name:
C:\Program
Files\MATLAB\R2015b\toolbox\stateflow\stateflow 
> In restoredefaultpath (line 52)

And nothing changed. What is the meaning, please ? And what should I do next ?

Anıl