sum first matrix and second matrix

I want to collect the first function and the second function but there is an error there is no help ('Xf ').

x=[-1 8 2 -3 -5  6 -4 5 -8 7 -9 4 5 -10 -6 -11 8 3 7 1 -5 -20 14 18 19 -16 8 16 -17 -15];
Xp=x(x>0);
Xn=x(x<0);
figure(1)
stem(Xn);
title('negative signal');
Xn=abs(Xn);
figure(2)
stem(x);
title('orginal signal');
figure(3)
stem(Xp);
title('positive signal');
figure(4)
stem(Xn);
title('abs negative signal');
Xf=Xp+Xn;

Answer 1

[Walter Roberson]

Your Xp and Xn are different lengths. You cannot add them. And if you could, what would the answer mean ?

[abdullah qasim]

I have a signal when I separate the positive signal from the negative signal as shown above

the matrixes dimension are diffrent

then must be transmitted this matrixes

[Walter Roberson]

Okay, so transmit them. Just keep in mind they are different lengths.

You can concatenate them if you have reason to,

[Xn, Xp]

but you would need to keep track of the size of at least one of the two if you need to separate them out again.

[abdullah qasim]

How can I keep track of the size of at least one of the two if I need to separate them out again?

[Walter Roberson]

XNsize = length(Xn);
[XNsize, Xn, Xp]