function al=pmat2(mx,my,h)
% PMAT2 Generate the matrix for the 2D Laplacian
%
n=mx*my;
hx=h; hy=h;
h2=h^-2;
offdx=-1*h2*ones(n,1);
offdy=-1*h2*ones(n,1);
dd=4*h2*ones(n,1);
al=spdiags([offdy, offdx, dd, offdx, offdy], [-mx, -1,0,1,mx],n,n);
for i=1:my-1 
p=i*mx;
al(p,p+1)=0;
al(p+1,p)=0;
end