Integrating a matrix with symbolic values

For a finite element method I have to perform a double integration to find the stiffness matrix. First using a function 'matrices' I set up the matrix 'stiffness'. This is an 8x8 matrix with the ymbolic values of 's' and 't' in it. I would then like to integrate w.r.t to both variables over a region of -1 to 1.

 D = E*[1,v,0;
    v,1,0;
    0,0,0.5*(1-v)];

 x6 = [0 1 2 0];
 y6 = [0 0 2 1];

 syms s
 syms t
 [J,A,M,B] = matrices(s,t,x6,y6);

 stiffness = te*transpose(B)*D*B*det(J);

 stuff = @(s,t) stiffness

K = integral2(stuff,-1,1,-1,1)

This gives me the following error: Input function must return 'double' or 'single' values. Found 'sym'.

How can I integrate this matrix with symbolic values?

Answer 1

[Areej Varamban Kallan]

Hi Lars,

Please see the answer in this link to understand the method of performing double integration on symbolic arrays.