Unnest cell array with nested cells to a cell array

Question

Federico Canè 2014-10-20

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https://ww2.mathworks.cn/matlabcentral/answers/159371-unnest-cell-array-with-nested-cells-to-a-cell-array

评论： Simon Matte 2020-10-12

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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Answer 1

Sean de Wolski 2014-10-20

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% Sample Data
C = repmat({num2cell(1:11,1)},100,1);
% Unpacked
C2 = vertcat(C{:})

Unpack ( {:} ) it and use comma-separated list expansion in vertcat.

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Boris 2017-7-29

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 2017-7-29

编辑：Boris 2017-7-29

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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...

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Answer 2

Gabor Bekes 2019-11-11

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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).

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Simon Matte 2020-10-12

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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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