Well, if you want to draw three different graph figures into one figure then you can use subplot.
ex: let say I have two graphs and I want them to see adjacent.
subplot(1,2,1), plot([1:10]);
subplot(1,2,2), plot([11:2:30]);
or if you want three different graph only in one figure then doc hold as Grzegorz suggest above.
ex
plot([1:10],'r'); hold on;
plot([11:2:30],'b');
