How to draw the magnitude of displacement ?

Hi, i want to plot the magnitude of tip displacement x(:,1) in function of rload but i obtain zeros. I don't know where is the problem such as x(:,1) in function of rload is harmonic function.

index=1;

for i= 0:20:50000

xs = sum(x(:,1).^2);

xrms = sqrt(xs /(numel(x(:,1))+1));

xtrms(index) =xrms;

index= index + 1; end

figure;

plot([0:20:50000],xtrms,'r')

xlabel('rload(Ohm)');

ylabel('magnitude of tip displacement(m)');