Unrecognized function or variable

Hello. I wrote an example of the diskmarginplot function in Matlab 2019Rb version, but it gives an error. Please help me.

[DGM]

Where is diskmarginplot.m? Did you add it to the path or place it in a directory that's on the path?

Answer 1

[Sam Chak]

Hi @Aysel Alimirzayeva

It requires Robust Control Toolbox, the function is introduced in R2020a. Since yours is R2019b, then I think ...

https://www.mathworks.com/help/robust/ref/lti.diskmarginplot.html

s = tf('s');
G = 0.38*(s^2 + 0.1*s + 0.55)/(s*(s + 1)*(s^2 + 0.06*s + 0.5))

G =
 
     0.38 s^2 + 0.038 s + 0.209
  ---------------------------------
  s^4 + 1.06 s^3 + 0.56 s^2 + 0.5 s
 
Continuous-time transfer function.

diskmarginplot(G)

[Aysel Alimirzayeva]

@Sam Chak Thank you very much.