Re: rlocus

[Andrei]

ro in your case is the graph, that is plotted.
the rlocus function returns multiple roots of the system and graph with 
different gain (K),
if you want a specific root, you should use the feedback function for a 
closed loop, convert the system form to a transfer function and get the 
roots of the denominator:
octave:1> n=1; d=[1 3 2 0];
octave:2>[num,den]=feedback(tf(n,d),tf(1,1));
octave:3>roots(den)
ans =
   -2.32472 + 0.0000i
   -0.33764 + 0.56228i
   -0.33764 - 0.56228i



Eduardo Adam wrote:

> Hi everyone,
>
> I'm sorry for this basic question but I'm a new octave user and, I'm 
> accustumed to used matlab.  So, I ran the following comands:
>
> octave:1> n=1; d=[1 3 2 0];
> octave:2> [ro,Kr]=rlocus(tf(n,d),0.1,0,10)
> warning: in /usr/share/octave/2.1.73/m/control/base/rlocus.m near line 3, 
> column 8:
> warning: rlocus: some elements in list of return values are undefined
> ro = [](0x0)
> Kr =
>
>  -0.38490
>   0.38490
>
>
> My question is, why I have the answer ro=[]?
> I'm interested in the closed loop roots and, according to the help, rlocus 
> would have to provide the roots
>
> On the other hand, the comand 
> octave:3> rlocus(tf(n,d),0.1,0,10)
>
> it works perfectly.
> My octave version is 2.1.73 and I'm working with linux-kubuntu.
>
>
> Thanks to everyone.
>
> Eduardo
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