for loop and data storing

Hi I am contacting because I need some help with matlab code. I am a quite new user, I need to store the data in an array. I have a plot Y versus the time (tfinal =m) and the Y value is calculated n-times from a n-loop. I need to store the data in mxn array. at the moment I am able to store just 1xn vector, loosing the information on the time. The part of the m.file are the following

index=0
for i=1:Loop
   t=0; %start time 
   t_end=40; %end time
   t_sample=1; %sample interval for gathering data
   ........
   j=1; 

    t_ar(1,t_end/t_sample+1)=0; 
    t_ar(1,j)=t; 
    Y1_ar(1,t_end/t_sample+1)=0; 
    Y1_ar(1,j)=Y1; 
    etc etc
end

Now, I have use this

m =Loop; 
n=t_end; 
Mat = zeros(m,n); 
for i = 1:m 
for j = 1:n 
Y4_array(i,j) = Y4;% what ever end end

at the end of the n-loop and if I try to visualize Y4_array(i,j) I can see and array filled with with one number, that I think it is the last one recorded. What do you think? Could you help me? Cheers carmen