Need help with triangular wave

figure(1)
t=-5:0.5:5;
xcos=cos(pi*2*t);
xpsqw=xcos>0;
plot(t,xpsqw);
xlabel('Timp(s)');
ylabel('Amplitudine')
title('Graficul functiei u(t)')
ylim([-3.5 4.5]);

This is my code, but I do not know how to modify it to look like this