function af=Aflat(X)
%Approximate Flatness

n=size(X,2);
c=sum(X,2)/n;
A=(X-c*ones(1,n))*X';
[V,D]=eig(A);
[Dmin,I]=min(diag(D));
d=V(:,I)'*(X-c*ones(1,n));   
af=max(d)-min(d);