Center difference matric A

function A=GEA(m)
h=1/m+1;
X=linspace(0,1,m);
x=sin(X(2:m));
A=zeros(m,m);

for i=1:m
    A(i,i)=-2;
    if i-1 ~= 0
        A(i,i-1)=1;
        A(i-1,i)=1;
    end
end
A=(1/h^2)*A;