%This code will plot three lines on same plot.
x1=[2 3 4 5 6 8 10];
y1=[9 4 3 2 7 4 2];
x2=[11 20 30 50 60 50 40];
y2= [20 30 50 60 20 30 10];
x3=[2 3 4 5 8 6 4];
y3=[9 4 3 2 4 6 8];
plot(x1,y1,'r')
hold on
plot(x2,y2,'g')
hold on
plot(x3,y3,'b')
hold off