how to get variable value in plot automatically

how to get a plot displaying value of gain and corresponding responce in single figure as shown in attached image

[Alex Mcaulley]

See this: legend

Answer 1

[KSSV]

x = 0:10 ; 
figure
hold on
for i = 1:3
    y = i*x ; 
    plot(x,y)
end
legend

OR

x = 0:10 ; 
figure
hold on
for i = 1:3
    y = i*x ; 
    plot(x,y)
    str = ['k=',num2str(i)] ; 
    text(mean(x),mean(y),str)
end