Please refer to the last two lines of the code:
err_every_iter = iter_error; % iter_error is stored here
err_every_iter = [1:n]; % again err_every_iter is replaced with [1:n]
Here, you are updating the values in 'error_every_iter' twice (read the comments above). I think as per your requirement, you need 'err_every_iter' array which you need to update inside the 'for loop' for every iteration as follows:
err_every_iter(i) = iter_error % i represents the iterator of for loop
Hope this will help.
