how can i create a loop for this pattern

Sorry for asking a seemingly dumb question however it has been doing my head in! I am simulating asset paths in a Monte-Carlo simulation and I am trying to get the 1 year return for each year separately stored in a variable rt. I tried to create a loop for the rt1-rt4 variables so I could do this for all 10 years that I am simulating however I've spent way too much time fiddling around!

I was hoping that someone could point me in the right direction. I've had similar problems like this before and am avoiding a brute force method.

Thank you for your time!

timesteps = 252;
years = 10;
draws = timesteps*years;    
epsilon = randn(1,252); 
sigma = 0.2;

    for j = 1:draws
                tsr(j) = exp(( - 0.5 * sigma^2) * ...
                    (1/timesteps) + epsilon(j) * sigma * ...
                    sqrt(1/timesteps));
    end

    % first year
    yr1cumret = cumprod(tsr(1,1:timesteps));
    yr1ret = yr1cumret(1,end);
    rt1 = log(yr1ret);

    % second year
    yr2cumret = cumprod(tsr(1,timesteps+1:timesteps*2));
    yr2ret = yr2cumret(1,end);
    rt2 = log(yr2ret);

    % third year
    yr3cumret = cumprod(tsr(1,timesteps*2+1:timesteps*3));
    yr3ret = yr3cumret(1,end);
    rt3 = log(yr3ret);

    % fourth year
    yr4cumret = cumprod(tsr(1,timesteps*3+1:timesteps*4));
    yr4ret = yr4cumret(1,end);
    rt4 = log(yr4ret);

    rt = [rt1, rt2, rt3, rt4];

Answer 1

[Andrei Bobrov]

I'm corrected my code.

Maybe so?

ts = 252;
years = 10;
d = ts*years;    
epsilon = randn(1,d); % !!!!!!!!! here fixed
sigma = 0.2;

f = 1/ts;
jj = reshape(1:d,ts,[]);
tsr = exp(-.5*sigma^2*f + epsilon(jj)*sigma*sqrt(f));
rt = reshape(log([tsr(1,:);prod(tsr)]),1,[]);

[Andrei Bobrov]

Corrected.

[H Flem]

Thank you for that. for the rt variable it is returning a 1x20 vector.

Sorry for my ignorance but I am having trouble understanding what exactly is going on here.