Hi Alexander - we're getting somewhere now! I installed gnuplot. However, the graph I'm getting is rather ugly... I tried switching to fltk and it did not change the output. Either way, I get an all text output. I used octave with the controls toolbox a few years ago and I remember getting nice looking graphs that popped up in an external window - do you have any idea how to set this up?
octave:1> pkg load control octave:2> a = tf(1, [1 2 3])
Transfer function 'a' from input 'u1' to output ...