Try this code:
for i = 1:4
subplot(2, 2, i)
plot(rand(1, 10));
end
axes('Units','Normal','Position',[.075 .075 .85 .85],'Visible','off');
set(get(gca,'Title'),'Visible','on')
title('global title','FontWeight','bold','FontSize',15);
or use one of these function from fex:
