How do i add legend

HI all i am just willing to add legend to the above figure where i just wana involve legend for x1 and data 1 what is the command to type that . this is an SMC controller.

Answer 1

[Lizhou]

x = linspace(0,pi);
y1 = cos(x);
p1 = plot(x,y1);

hold on
y2 = cos(2*x);
p2 = plot(x,y2);

y3 = cos(3*x);
p3 = plot(x,y3);
hold off

legend([p1 p3],{'First','Third'})

Answer 2

[Emmanuel Adesina]

You can simply plot all as:

plot(x,y1, x,y2, x,y3, ...)

or

line(x,y1)
line(x,y2)
line(x,y3)
...

and add all legend at once.

legend("y1","y2","y3",...)