Analysis of the stability of the system characterized by the transfer function

Hi all,

I also have a problem to solve in the field of "systems theory". I solved the mathematical part, but now I have to find a virtual method for analyzing the stability of the system characterized by the transfer function. Therefore, I chose matlab.

I need to graphically display the Nyquist diagram and the poles and zeros of the transfer function.

Transfer function:

The code for the Nyquist diagram is as follows:

num=[1 1]
den=[1 1 4 1 2]
G=tf(num,den)
plot(nyquist(G))
grid on

The code for representing the poles and zeros of the transfer function is as follows:

num=[1 1]
den=[1 1 4 1 2]
G=tf(num,den)
plot(pzmap(G))
grid on

How could I see on the same graph both functions or one below the other?

Thank you in advance

Answer 1

[Paul]

Does this do what you want:

>> nyquist(G)
>> [P,Z]=pzmap(G);hold on;plot(real(P),imag(P),'x'),plot(real(Z),imag(Z),'o')