problem in matlab programs

Hi, I'm having problem to plot my figure when i try to run the program several times to get an average value of rmse. I know there is something wrong the way i save the data for plotting, but i dont know how to solve it.

if i set the no_of_runs more than 1,let say 2 the previous data will still be there and making the data save in the xArray much bigger (1x201), hence the vector of t (1x101 double) and xArray and others will not be the same any more and fail to plot.

how do i make the array will still be (1x101 double) everytime when no_of_runs more than 1? thank you.

tf = 100; % simulation length 
no_of_runs=2

 x=1;  %%initialize
xhatukf1Array = 1;
Pukf1= ..
Pukf1array = diag(Pukf1);

%%start program   
for k=1: no_of_runs
  for t=1:tf

 .....equations...+++
  x= ...
  z=.... 
  Kukf1 = Pxy1 /(Py1);
  xhatukf1 = xhatukf1 + Kukf1 * (z - zhat1);
  Pukf1 = Pukf1 - Kukf1 * Py1 * Kukf1';    

    % Save data for plotting.

   xArray = [xArray x];
   xhatukf1Array = [xhatukf1Array xhatukf1];
   Pukf1array = [Pukf1array diag(Pukf1)];

end %%(end t loop)

t = 0 : tf;
figure;
plot(t, xArray(1,:),'k-',t,xhatukf1Array(1,:),'m');
xlabel('Seconds');
legend('True Position','ukf2n+1');

rmsError_ukf2N(k)     = sqrt(inv(tf)*sum((xArray-xhatukf1Array).^(2)));

end %%(end k loop)

Answer 1

[Jan]

for k=1: no_of_runs
  xArray = [];
  ...
end

A pre-allocation would be more efficient:

for k=1: no_of_runs
  xArray = zeros(<LENGTH_OF_x>, tf);  % I do not know "size(x)"
  for t=1:tf
    xArray(:, t) = x;
  end
end

[dab483]

thank you so much.. now i can plot when no_of_runs more than 1. :)