[MATLAB毕业设计] 请问各位大师，我这个程序的问题在哪儿

[zyl0303]

syms t1 t2;
N=100;
L=0.5;
dx=L/(N-1);
i=sqrt(-1);
u=1.257*10^(-6);
e=8.854*10^(-12);
o=2*pi/sqrt(u*e);
k=o*sqrt(u*e);
JJ=zeros(1,N-1);

for n=1:N-1
if n==1;
J1(n)=0*t1;
JJ1(n)=subs(J1(n));
J2(n)=(((n*dx-t1)./dx).*exp(-i*k*sqrt(t1-t2).^2))./(4*pi*sqrt(t1-t2).^2);
JJ2(n)=subs(J2(n));
else
J1(n)=(((t1-(n-2)*dx)./dx).*exp(-i*k*sqrt(t1-t2).^2))./(4*pi*sqrt(t1-t2).^2);
JJ1(n)=subs(J1(n));
J2(n)=(((n*dx-t1)./dx).*exp(-i*k*sqrt(t1-t2).^2))./(4*pi*sqrt(t1-t2).^2);
JJ2(n)=subs(J2(n));
end
end

下面是程序报错：
??? The following error occurred converting from sym to double:
Error using ==> mupadmex
Error in MuPAD command: DOUBLE cannot convert the input expression
into a double array.

If the input expression contains a symbolic variable, use the VPA
function instead.

Error in ==> QUADmn at 21
JJ1(n)=subs(J1(n));
我是新手，请各位大师能够在百忙之总给予指点，本人感激不尽！！！