cell array into 3d matrix

i have a cell array of size 104x104 with each cell having a matrix of size 1x1000. How can i convert this cell into a 3d matrix of size 104x104x1000 ??

[Sean de Wolski]

+1, good clear question with room for many good approaches

Answer 1

[Hanan Shteingart]

You can concatenate cell array content using the "cat" function with this syntax: cat(dim, A{:}) where A is your cell array

Answer 2

[the cyclist]

Both of these should do the same thing (and I think it is the thing you want). The second is a little bit more transparent, but slower.

B1 = cell2mat(arrayfun(@(x)permute(x{:},[3 1 2]),A,'UniformOutput',false));

B2 = zeros(104,104,1000);
for i = 1:104,
for j = 1:104,
    B2(i,j,1:1000) = permute(A{i,j},[1 3 2]);
end
end

[Sean de Wolski]

Reshape() instead of permute() for speed.

Answer 3

[Sean de Wolski]

Or the pure matrix manipulation approach:

%Sample Data:
X = reshape(magic(50),1,[]);
C = cell(100,100);
C(:) = {X}; %100 x 100 cell array of xs

%Engine:
D = reshape(reshape(cell2mat(C)',numel(X),numel(C))',size(C,1),size(C,2),numel(X)); %some reshapin'

%Check
all(all(all(bsxfun(@eq,D(1,1,:),D)))) %Is it right?

yay!

Answer 4

[Andrei Bobrov]

permute(reshape(cell2mat(C).',numel(C{1}),size(C,2),[]),[3 2 1])

or

reshape(cat(1,A{:}),[size(C), numel(C{1})])