MATLAB: Error with Subs Function

MATLABsubsfunctionsubstitution

I using the following code to create a grid of the values for equation SF with numnerical values for x1 and x2 but have encountered the following error…
Error using symengine
Division by zero.
Error in sym/subs>mupadsubs (line 160)
G = mupadmex('symobj::fullsubs',F.s,X2,Y2);
Error in sym/subs (line 145)
G = mupadsubs(F,X,Y);
Error in Orthogonality_Check (line 51)
S2(i,j)=subs(S1(i),x2,iX1(j));
When I compute each value separately I do not have a problem, any advice would be appreciated thanks!
P.S values in grid are expected to be zero is this the cause of the problem?
% - Define variables
x1  = sym('x1');
x2  = sym('x2');
% - =======================================================================


% - Define dU and fu and create orthogonality function
f  = [-1+9*x1-2*x1^3+9*x2-2*x2^3; 1-11*x1+2*x1^3+11*x2-2*x2^3];
dU = [2*x1^3-10*x1+x2+1;2*x2^3-10*x2+x1];
fu = f+dU;
Org = dU'*fu;
% - =======================================================================
% - Integrate orthogonal function
SF = int(Org);
% - =======================================================================
% - Set Limits for x1,x2...
LMB = 2;
n = 10;
iX1 = linspace(-LMB,LMB,n+1);
iX2 = linspace(-LMB,LMB,n+1);
for i=1:length(iX1)
    S1(i)=subs(SF, x1,iX1(i));
       for j=1:length(iX1)
        S2(i,j)=subs(S1(i),x2,iX1(j));
    end
end

Best Answer

You did not specify the variable of integration for Org. int() uses symvar to guess that x1 should be used. The integral has division by x2. When x2 is 0 that is problem.
Instead of using subs, you might want to use limit, as the limit as x2 approaches 0 is 0.
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