Re: problem with the bode function

[Lukas Reichlin]

On 07.12.2011, at 14:11, Laurent Tissier wrote:

> Hello,
> 
> yesterday I have updated the control toolbox (ver 2.2.2) and now the 
> following command  fails:
> 
> H=tf([1 0 1],[1 1 1]);
> bode(H)
> 
> I work under ubuntu 10.10 with octave 3.4.

Thanks for your report. A few observations:
- The problem is also present with control-2.2.1.  --> not related to version 
2.2.2
- [mag, pha, w] = bode (H) doesn't hang ---> looks like a plotting problem
- both Fltk and Gnuplot graphics backends are affected
- H=tf([1 1 1],[1 1 1]) gets plotted ---> The zero for s^1 in the numerator 
seems to cause the problem
- H = tf (1, [1, 0, 1]) hangs too ---> there must be a problem with complex 
conjugate pole or zero pairs when their real part is 0.
- Plotting mag, pha and w from point 2 works ---> hmm…
- Commenting out the two 'axis' commands in bode.m gets your example working
- The variable ax_vec_mag contains infs and nans when octave hangs --> I'll 
take care of __axis_limits__.m

I'll try to fix this and release control-2.2.3.

Regards,
Lukas