% sep6b

load airfoil

xy = [x,y];
n = max(j);
a = sparse(i,j,1,n,n);
figure(1);
clf
gplot(a,xy)
a = a + a'; a = a - diag(diag(a));
la = diag(sum(a)) - a;

[v,d] = eigs(la,3,'sm');
d
pause

figure(2);
clf
gplot(a,v(:,1:2))