Well, that is certainly possible... if you make the arrays large enough then there might just not be enough memory available.
Is it possible to predict the number of columns that will be needed for each Fn before doing the actual callculations? If so then you could consider doing that calculation and totaling them, and pre-allocating the output array, then writing directly into the output array instead of building the cell array. If you pre-build the sizes then you can use cumsum() to create an array that will tell you which indices to write at
As a side note: it is more efficient to use
F = horzcat(F{:});
than F = cell2mat(F); -- but this would not solve your memory problems.
