with 3 recommended.
% 
% After the initial setup phase, there are two different ways to actually compute 
% _Ax_ and _A^Ty_. The first, recommended, method is by using a MATLAB/Octave 
% class that is demonstrated in the initial examples in <https://github.com/villekf/OMEGA/blob/master/forward_backward_projections_example.m#L821 
% forward_backward_projections_example.m>, the second method is the old one using 
% functions.
% Class based examples
% First is a class-based exampled computing OSEM/MLEM estimat