plotting magnitude of vectors

I have two matrix of x= [1 250] and y= [1 250]. These are readings of signal which contains negative and positive values. I managed to plot the direction of the vectors using

quiver(n,s,x,y)

where n and s are the x and y locations.To plot the magnitude of the vectors. I used

 plot(time, sqrt(x.^2+y.^2));

But this only gives the magnitude(positive). Can somebody show me while to plot the magnitude of the vector which shows both negative and positives(based on direction)?

Thank you.