MATLAB: Subs not working for symbolic expressions

symbolic

I have the following code and want to evaluate s at x(1) and y(1) and store it to s in s(1). The expression worked fine when I was using
s1 = (fun,{x,y},{x1,y1});
I'm unsure why the following code is failing to run?
A = 39.3;
B = 19.7;
t = 0.1;
syms x y
pxysym = A*x-3*x^2-4*x*y;
qxysym = B*y-2*x*y-y^2;
pxsym = diff(pxysym,x);
pysym = diff(pxysym,y);
qxsym = diff(qxysym,x);
qysym = diff(qxysym,y);
sxsym = pxysym*pxsym+qxysym*qxsym;
sysym = pxysym*pysym+qxysym*qysym;
x = zeros();
y=zeros();
x(1) = 5
y(1) = 5
ssym=0.5*(pxysym^2+qxysym^2);
s(1) = subs(ssym,{x,y},{x(1),y(1)})
TIA

Best Answer

Look at the output of the following command executed immediately before your subs call.
whos
Is x a symbolic variable at that point? What in your symbolic expression is your subs call actually trying to replace?
I would change the name of the variable containing the numeric values you want to substitute into your symbolic expression to something else, like "xx = 5". Then substitute the value of xx for the symbolic variable x.
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