rlocus

[Eduardo Adam]

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