Combine a cell array of cell arrays to a cell array of numbers

Hi,

I have a dynamic cell array of cell arrays and I want to combine it into a cell array of data.

For example:

kdata =

Columns 1 through 4

    {10x3 cell}    {10x3 cell}    {10x3 cell}    {10x3 cell}

Columns 5 through 8

    {10x3 cell}    {10x3 cell}    {10x3 cell}    {10x3 cell}

Columns 9 through 10

    {10x3 cell}    {10x3 cell}

What I want:

kdata_combined =

Columns 1 through 11

    '8'    '7'    '2'    '8'    '10'    '5'    '1'    '2'    '1'    '4'    '3'
    '2'    '1'    '4'    '2'    '3'     '0'    '3'    '3'    '0'    '0'    '0'
    '1'    '1'    '1'    '4'    '4'     '4'    '1'    '1'    '2'    '4'    '2'
    '3'    '2'    '1'    '1'    '2'     '1'    '1'    '1'    '0'    '2'    '2'
    '2'    '5'    '0'    '0'    '1'     '2'    '0'    '2'    '0'    '1'    '0'
    '0'    '1'    '3'    '1'    '1'     '2'    '1'    '0'    '0'    '2'    '1'
    '0'    '4'    '0'    '0'    '1'     '0'    '1'    '2'    '1'    '1'    '0'
    '2'    '0'    '0'    '0'    '0'     '0'    '0'    '0'    '1'    '0'    '0'
    '2'    '0'    '0'    '1'    '0'     '1'    '2'    '0'    '0'    '3'    '0'
    '0'    '0'    '1'    '0'    '1'     '0'    '1'    '0'    '2'    '2'    '1'

Columns 12 through 22

    '11'    '0'    '2'    '11'    '6'    '7'    '6'    '0'    '5'    '0'    '4'
    '2'     '7'    '2'    '1'     '1'    '4'    '6'    '2'    '0'    '5'    '3'
    '2'     '1'    '1'    '1'     '1'    '4'    '3'    '1'    '2'    '3'    '0'
    '2'     '1'    '2'    '1'     '1'    '4'    '0'    '1'    '0'    '1'    '2'
    '2'     '0'    '1'    '1'     '1'    '0'    '2'    '1'    '1'    '1'    '3'
    '0'     '0'    '0'    '3'     '0'    '4'    '0'    '0'    '0'    '0'    '1'
    '3'     '2'    '1'    '2'     '2'    '0'    '2'    '0'    '0'    '0'    '1'
    '2'     '0'    '3'    '0'     '1'    '2'    '0'    '2'    '1'    '1'    '0'
    '1'     '0'    '1'    '1'     '0'    '0'    '2'    '0'    '2'    '0'    '0'
    '0'     '0'    '0'    '2'     '2'    '0'    '1'    '3'    '0'    '0'    '0'

Columns 23 through 30

    '1'    '1'    '3'    '1'    '2'    '4'    '5'    '8'
    '0'    '0'    '5'    '4'    '0'    '2'    '2'    '7'
    '1'    '1'    '3'    '9'    '0'    '0'    '4'    '0'
    '3'    '1'    '1'    '0'    '3'    '0'    '0'    '1'
    '3'    '1'    '0'    '0'    '0'    '1'    '1'    '0'
    '3'    '1'    '0'    '1'    '0'    '1'    '0'    '2'
    '1'    '0'    '0'    '1'    '1'    '0'    '1'    '0'
    '7'    '1'    '0'    '0'    '0'    '1'    '1'    '1' 
    '0'    '0'    '2'    '1'    '2'    '0'    '3'    '1' 
    '4'    '0'    '1'    '0'    '2'    '0'    '2'    '0'

I want to do this without any 'for' because my cell arrays are too big. And I can't concat them manually because I never know the size.

Is there anyway I can do this using some function like cell fun ?

Thanks.

[per isakson]

How do you know they "are too big" to use a loop?

Answer 1

[Matt J]

 kdata_combined = cell2mat(kdata)

[Eduardo]

Did not work for me

Error using cell2mat Cannot support cell arrays containing cell arrays or objects.

[Matt J]

Make that,

kdata_combined = cell2mat([kdata{:}])

[Eduardo]

Thanks, Matt. But there is another error

Error using cat CAT arguments dimensions are not consistent.

Error in cell2mat (line 84) m{n} = cat(1,c{:,n});

I don't understand why. The dimensions of my cell arrays are all 10x3 or (any number)x3

[Matt J]

The dimensions of my cell arrays are all 10x3 or (any number)x3

@Eduardo,

You should modify your posted example, clarifying the data you have. All of your cells there are 10x(any number) not (any number)x3. You cannot horizontally concatenate (as you have in your example) when you have varying numbers of rows.

[Eduardo]

I usually have 1 cell array with 5, 10 or any number of cell arrays in it.

Every one of them are like 4000x3 or 4000x2. But they're all the same size. My example was wrong, sorry about that.

I attached a real .mat file with one cell array.

[Matt J]

Just do

 kdata_combined=[kdata{:}];

Answer 2

[John Thompson]

   % Initialize fake data
   cellA = cell(10,1);
   for i = 1:10
       cellA{i} =  num2cell(round(rand(10,1)*10));
   end

   % RUN THIS to extract and realign nested cell arrays
   cac = cell2mat(cellfun(@(x) cell2mat(x)' , cellA, 'UniformOutput', false));

Answer 3

[per isakson]

You have a cell array of cell arrays of strings. Your strings consist of one and in some cases two characters. The solution, which I proposed, assumed that all strings are of the same length. Since they are not you get the error

    Error using cat
    Dimensions of matrices being concatenated are not consistent.
    Error in cell2mat (line 84)
                m{n} = cat(1,c{:,n});

.

I missed the word "number" in the topic title.

Does this do the job?

    cac = cat( 2, kdata{:} );
    num = str2double( cac );
    cac_num = num2cell( num );

or this

    kdata_combined = cat( 2, kdata{:} );

both assume that kdata is .< 1 xn cell>

.

[Later]

and when kdata is .< m xn cell>

    cc = repmat( kdata, 400, 1 ); 
    tic
    nrows = size( cc, 1 );
    cac = cell( nrows, 1 );

    for jj = 1 : nrows
        cac{ jj } = cat( 2, cc{ jj, : } );
    end

    kdata_combined = cat( 1, cac{:} );
    toc
    whos('kdata_combined')

returns

    Elapsed time is 0.108852 seconds.
      Name                     Size                Bytes  Class    Attributes

      kdata_combined      114800x24            314099200  cell

.

I don't think you will find a non-loop solution that is faster

[Eduardo]

I want the result like this:

examples = {{'1','12'},{'2','4'},{'7','10'},{'0','3'}}

example =

    {1x2 cell}    {1x2 cell}    {1x2 cell}    {1x2 cell}

result =

    '1'    '12'    '2'    '4'    '7'    '10'    '0'    '3'

This example has just one row, my real data usually have a lot of rows.