Hey Hardeep,
After a quick glance, I am seeing a few possible errors in your code. Because of the way you are populating "W1" and "W2" and your description of wanting 10,000 time steps per year, I am assuming that you are wanting "N" number of elements per year for a total of "T" years. Therefore, you want length(t) = N*T and you want the elements of "t" equally spaced between 0 and T-1.
If these assumptions are correct, you need to delete the following two lines of code.
t = (0:30:1); % Note that this line will result in "t=0"
t = t*T;
Then, in place of the first line of code that you deleted, insert the following line of code.
t = linspace(0,(T-1),T*N)';
If the above is correct, you also need to update your calculations of W1 and W2.
W1 = [0; cumsum(randn(T*N-1,1))]/sqrt(T*N);
W2 = [0; cumsum(randn(T*N-1,1))]/sqrt(T*N);
If it helps, there are examples of implementing "Brownian Motion" models at the bottom of the documentation at the following link.
