That is because w is a cell array of cell arrays.
For example:
x = rand(16);
J = 1;
[Faf, Fsf] = FSfarras;
[af, sf] = dualfilt1;
w = dualtree2D(x, J, Faf, af);
w{2}{1} gives you the approximation image at level 1, so you can do:
App = w{2}{1};
The above is matrix
To get the dual tree detail coefficients (H,V,D),enter:
Atreedetcoefs = w{1}{1};
Btreedetcoefs = w{1}{2};
The above are cell arrays of matrices, you can use cell2mat on Atreedetcoefs and Btreedetcoefs, but you have to be careful that you know how the H,V, and D matrices are concatenated.
