The following octave commands:
plot(x,[ymat(:,[1,2,4])],{"k-.","k-","k:"},"linewidth", 2)
set(gca,'fontsize',26)
axis([1,6,-20000, 120000])
title(['Health People with minimum t-norm for dpercent=0.05'])
xlabel('time interval (month)')
ylabel('People (in thousands)')
yticklabels({"-20","0","20","40","60","80","100","120"})
legend ({"upper bound", "modal value", "lower bound" }, "location", "northeast")
grid on
produce the graph:
