why ii = 2:z_points ?

[landieyun]

Hi all:

 Does anyone know why the step number ii begin from 2 not from 1? thanks so much.

%% Run the step function over each step
tic
for ii = 2:z_points
% Print the step number if verbose
if sim.verbose
t_in_loop = tic;
disp(ii)
end

[AaHaHaa]

"ii=1" represents the starting point of the fiber. The solver uses the information of the previous z_point to solve for the next z_point and thus ii starts from the next point of the starting point, which is ii=2, to the end.