plot or stem the length of negative and positive signal?

I follow positive and negative references

XNsize = length (Xn);

[XNsize, Xn, Xp]

I want to plot the signal by using "stem" as follow

stem([XNsize, Xn, Xp])

but in different colours

meaning

Xn in red

Xp in blue

Answer 1

[KSSV]

y1 = rand(10,1) ;
x1 = 1:length(y1) ;
y2 = rand(15,1) ;
x2 = [1:length(y2)]+length(y1) ;

figure
hold on
stem(x1,y1,'r')
stem(x2,y2,'b')
legend('x1','x2')

[abdullah qasim]

thank u very much

Answer 2

[madhan ravi]

stem(repmat(XNsize,XNsize,1),[Xn, Xp]) 

[abdullah qasim]

thank u .

but this method not working