3 D plot of transfer function magnitude with complex axis

I am trying to plot the following transfer function's magnitude on a third(z) axis, however it contains a pole and the graph I am getting is obviously incorrect: s+1/s+2. Also i am getting the following warning, matrix is close to singular . My code is:

>> x=linspace(-10,10);

>> y=linspace(-10,10);

>> [X,Y]=meshgrid(x,y);

>> Z=abs((X+i*Y+1)/(X+i*Y+2));

Warning: Matrix is close to singular or badly scaled. Results may be inaccurate.

RCOND = 2.503334e-20.

>> surf(X,Y,Z)

>> rotate 3d on;

Answer 1

[Star Strider]

You forgot to do element-wise division (using (./) instead of (/)).

This works:

x=linspace(-10,10);
y=linspace(-10,10);

[X,Y]=meshgrid(x,y);

Z=abs((X+i*Y+1)./(X+i*Y+2));

figure(1)
surfc(X, Y, Z)
grid on
xlabel('Real')
ylabel('Imaginary')
view([30  30])

I rotated the plot (using the view function) so you can see the zero as well as the pole.

[Nirbhay Thacker]

Thanks! I was able to get the same result yesterday using sysms and fsurf. Now i can use your method for all other plots too.

[Star Strider]

My pleasure!