hello, this is a trivial question, m new to matlab. So please help me in this. It says "Input argument "D1" is undefined." code for cascading of two systems.

function [A,B,C,D,pmr]=cas(N1,D1,N2,D2)

r=length(D1);
norder= r-1;
[a1,b1,c1,d1]=tf2ss(N1,D1);
[a2,b2,c2,d2]=tf2ss(N2,D2);

A= [a1 zeros(norder); b2*c1 a2];
B= [b1; b2*d1];
C= [d2*c1 c2];
D= [d2*d1];

x=horzcat(A,B);
y=horzcat(C,D);
pmr= vertcat(x,y);

end

Answer 1

[the cyclist]

How are you calling the function cas when you use it?

If you are calling it with only one input argument, then D1 is going to be undefined.