y=[0 0; 4 4; -4 4; -4 -4;4 -4]; 
[K,d]=size(y);
X=[ ];
for i=1:K
    Xi=randn(20,2) + ones(20,1)*y(i,:);
    X=[X;Xi];
end
plot(y(:,1),y(:,2),'ro');
hold on; plot(X(:,1),X(:,2),'.');
