Unnest cell array with nested cells to a cell array
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Federico Canè
on 20 Oct 2014
Commented: Simon Matte
on 12 Oct 2020
How do I expand out an array with dimension '<100x1 cell>' in which each cell has a dimension '<1x11 cell>' into an array with dimension '<100x11 cell>'. Surely this must be straightforward? Thx
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Accepted Answer
Sean de Wolski
on 20 Oct 2014
% Sample Data
C = repmat({num2cell(1:11,1)},100,1);
% Unpacked
C2 = vertcat(C{:})
3 Comments
Boris
on 29 Jul 2017
Doesn't appear to work if the cell array contains cell arrays of empties ([]). Gives a single 1 column vertical cell array with most (but crucially not all) the elements......
Im my case, mycellarray has 1 x 26 cell array. Each of these cell arra6 has 709 by 1 cells. Several of these cell arrays are empty, some are partially empty. vertcat --> a cell array with 17018 x 1 cells, each with a single entry (many blank). However, 26*709 is 18434, not 17018...
Furthermore, if I transpose mycellarray (26 x 1 cells) then vertcat, I get the same result (17018 x 1 cells)... Must be hitting some kind of limit, I guess. Pity, as it is a pain to concatenate each cell array in mycellarray in a loop (or similar)...
Boris
on 29 Jul 2017
Edited: Boris
on 29 Jul 2017
Of course, it helps if you check that all the entries in the cell array are all cell arrays!
I had two cell array entries that were themselves arrays of doubles, not cell arrays and this is what was throwing the concatenation.
However, the very simple (horizontal) concatenation given by:
myflatcellarray=[mycellarray{:}];
seems to be marginally faster than horzcat...
More Answers (2)
Gabor Bekes
on 11 Nov 2019
You might want something along the lines of:
a2 = {{'asdf',{'asdf','asdf',{'asdf'},{'asdf'},{'asdf',{'asdf'}},'asdf'},{'asdf',{'asdf'},{{'asdf'}}}},'asdf'}
while any(cellfun(@iscell,a2))
a2 = [a2{cellfun(@iscell,a2)} a2(~cellfun(@iscell,a2))];
end
Now, you need to know in advance if you have a row, column or matrix layout cell array, and you need to use vertcat() for the latter two cases (logical indexing produces columns).
1 Comment
Simon Matte
on 12 Oct 2020
Stumbled on this by googling a similar situation, wanted to add:
The previous solution works, but it also re-orders the elements in your cell array. Since it mattered in my specific case, I used this variant for my application:
while any(cellfun(@iscell, a2))
idx = cellfun(@iscell, a2);
a2(idx) = a2{idx};
a2(~idx) = a2(~idx);
end
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