Вот пример:
figure
subplot(3,3,1), text(0.5,0.5,'1', 'FontSize',20)
subplot(3,3,2), text(0.5,0.5,'2', 'FontSize',20)
subplot(3,3,3), text(0.5,0.5,'3', 'FontSize',20)
subplot(3,3,4), text(0.5,0.5,'4', 'FontSize',20)
subplot(3,3,5), text(0.5,0.5,'5', 'FontSize',20)
subplot(3,3,6), text(0.5,0.5,'6', 'FontSize',20)
subplot(3,2,5), text(0.5,0.5,'7', 'FontSize',20)
subplot(3,2,6), text(0.5,0.5,'8', 'FontSize',20)