
h=1/3;
x=h:h:1-h;
y=x;
[X,Y]=meshgrid(x,y);
hold on;
plot(X(:),Y(:),'ro'); 
bordo=[0 0; 1 0; 1 1; 0 1; 0 0];
plot(bordo(:,1),bordo(:,2),'k-');

hold off;
plot([0 1/3 2/3 1 1 1 1 2/3 1/3 0 0 0],[0 0 0 0 1/3 2/3 1 1 1 1 2/3 1/3],'rs')
