How can I solve this ?

I have this code to generate the J1 matrix

syms r phi

r=sym('r','real'); 

phi=sym('phi','real');

N=zeros(3,3+2*nlayers);

Naux1=[1,0,0,r*sin(phi),-r*cos(phi);0,1,0,0,0;0,0,1,0,0];

N(:,1:5)=Naux1

J1=int(r*N'*N,r,R1,R2); 

J1=int(J1,phi,0,2*pi)

But I received this error message:

The following error occurred converting from sym to double:
Error using ==> sym.double at 29
DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use the VPA function instead.

What should I modify ?

Answer 1

[Star Strider]

You didn’t post ‘nlayers’, ‘R1’, or ‘R2’ so we can’t run your code. It is easy enough to integrate only ‘Naux1’ (substituting only it for ‘N=Naux1’ and using symbolic variables for ‘R1’, and ‘R2’).