S1 = [3 0; 0 0.001];
m1 = [0 0]';
X1 = mvnrnd(m1,S1, 1000);

S2 = S1;
m2 = [0 0.4]';
X2 = mvnrnd(m2, S2, 1000);

S3 = S1;
m3 = [0 0.8]';
X3 = mvnrnd(m3, S3, 1000);



figure(1)
scatter(X1(:,1), X1(:,2), 5, [0 0 0], 'filled');
hold on
scatter(X2(:,1), X2(:,2), 5, [0 0 0], 'filled');
hold on
scatter(X3(:,1), X3(:,2), 5, [0 0 0], 'filled');
hold off

 xlim([-5 5]);
 ylim([-5 5]);
set(gca, 'Visible', 'off')