Creating Table from Cell Array Data

Hi All,

I am trying to create a table from data stored in a Cell array . The cell array is 1x3 specified as follows:

SelectNewVectorCell = {[1;2;3;4;5;6;9;88], [11;22;23;25;66;88], [33;55;66;7;8;9]};

I then try to create the table using the following code. Unfortunately, I can only get it to output the final column of the cell array to the table (it seems to be overwriting…)

   le = length(SelectNewVectorCell)
   names(1,1:le) = {'Bin1'};
 
   rows1 = cellfun(@(M) size(M,1), SelectNewVectorCell);
   cols1 = cellfun(@(M) size(M,2), SelectNewVectorCell);
   maxrows1 = max(rows1)
  
    R = table();
    for K = 1 : length(SelectNewVectorCell) 
     R.(names{K}) = [SelectNewVectorCell{K}; nan(maxrows1 - rows1(K), cols1(K))];
    end

Interestingly if I change the code slightly to this it seems to work

   le = length(SelectNewVectorCell)
  % names(1,1:le) = {'Bin1'};
 
   names1 = {'Bin1', 'Bin2', 'Bin3'};
   rows1 = cellfun(@(M) size(M,1), SelectNewVectorCell);
   cols1 = cellfun(@(M) size(M,2), SelectNewVectorCell);
   maxrows1 = max(rows1)
  
    R = table();
    for K = 1 : length(SelectNewVectorCell) 
     R.(names1{K}) = [SelectNewVectorCell{K}; nan(maxrows1 - rows1(K), cols1(K))];
    end

Any ideas why the first code fails to write correctly to the table? Thanks

Ben

Answer 1

[Adam Danz]

The first version in your question doesn't work because "names" contain 3 VariableNames that are all "Bin1" so when you assign the values within the loop, the first iteration assigns Bin1 to the table but subsequent iterations overwrite that column since you're writing to the same variable name.

The second version of your question avoids that problem but naming the columns differently.

You can create that table with the 3 lines of code below.

SelectNewVectorCell = {[1;2;3;4;5;6;9;88], [11;22;23;25;66;88], [33;55;66;7;8;9]};

maxNumRow = max(cellfun(@(c) numel(c), SelectNewVectorCell));  % max length
mPad = cell2mat(cellfun(@(c){padarray(c,[maxNumRow-numel(c),0],NaN,'Post')},SelectNewVectorCell)); 

R = array2table(mPad, 'VariableNames', compose('Bin%d',1:size(mPad,2))); 

Result

R =
  8×3 table
    Bin1    Bin2    Bin3
    ____    ____    ____
      1      11      33 
      2      22      55 
      3      23      66 
      4      25       7 
      5      66       8 
      6      88       9 
      9     NaN     NaN 
     88     NaN     NaN 

For a list of concatenation methods for a cell array containing unequal matrix sizes, see this answer.