【求助】MATLAB请教：Index exceeds matrix dimensions错误！！！！

[dency]

MATLAB里的width.m文件如下：
出现 ???Index exceeds matrix dimensions错误，应该怎么修改？？？
function w = width( c )
[n,m]=size(c);
w = zeros(n,1);
x=[];
for i=1:n
for j=1:n
x(j)=(norm(c(i,-c(j,))^2;
end
a=sort(x);
b1=a(2);
b2=a(3);
w(i,=(b1+b2)/2^0.5;
end