I have a variable matrix sigma_xz with (x,y,z) variables and want to evaluate it for different values of (x,y) to get a new matrix with only variable (z). How can I do this?

clc;clear all;close all;
tic
syms x y z
D11=2.4804; D12=0.0543; D22=0.5419; D66=0.0792; w_11=1.278;
a=0.2;b=0.1;

w(x,y)=w_11*sin(pi*x/a)*sin(pi*y/b)
kx= diff(w,x,2);
ky= diff(w,y,2);
kxy= diff(w,x,y);
k=[kx;ky;kxy];
n=4 % #of layers 

Q_bar(:,:,1)=[155.7478    3.0153         0;
    3.0153   12.1584         0;
         0         0    4.4000]

Q_bar(:,:,2) =[12.1584    3.0153         0;
    3.0153  155.7478         0;
         0         0    4.4000]

Q_bar(:,:,3) =[12.1584    3.0153         0;
    3.0153  155.7478         0;
         0         0    4.4000]

Q_bar(:,:,4) =[155.7478    3.0153         0;
    3.0153   12.1584         0;
         0         0    4.4000]

digits(8) %specifying # of digits in output

for i=1:n
    sigma(:,1,i)=vpa(-z*Q_bar(:,:,i),7)*k;
end
vpa(sigma(:,:,:))

for i=1:n
dsigma_xz(i)=diff(sigma(1,1,i),x)+diff(sigma(3,1,i),y);
sigma_xz(i)=int(dsigma_xz(i),z);
end

vpa(dsigma_xz(:));
vpa(sigma_xz(:));

Answer 1

[KSSV]

x = pi/4 ;
sigma_xz = subs(sigma_xz,x) ;
y = pi/2 ; 
sigma_xz = subs(sigma_xz,y) ;

[Prateek jain]

thank you KSSV it works...

[KSSV]

Thanks is accepting & Voting the answer..:)