MATLAB/OCTAVE Extracting elements from different sized vectors in a cell array

Question

I have a simple question but I can\'t figure it out or find it anywhere. I have a cell array where c{1} is a vector and c{2} is a vector but of different lengths, up to c{i

Answer 1

In Matlab; without loops:

1. If the cell array contains column vectors and you want to arrange them into one big column vector:

   result = vertcat(c{:}); %// vertically concat all vectors
   

   Example:

   >> c = {[1;2], [1;2;3]};
   >> result = vertcat(c{:})
   result =
        1
        2
        1
        2
        3
   

2. If the cell array contains row vectors, you can arrange them as rows of a matrix, filling non-existent values with NaN (or any other value):

   M = max(cellfun(@numel, c)); %// max length of vectors
   c2 = cellfun(@(row)[row NaN(1,M-numel(row))], c, 'uni', 0); %// fill with NaN
   result = vertcat(c2{:}); %// concat all equal-size row vectors into a matrix
   

   Example:

   >> c = {[1 2], [1 2 3]};
   >> M = max(cellfun(@numel, c));
   >> c2 = cellfun(@(row)[row NaN(1,M-numel(row))], c, 'uni', 0);
   >> result = vertcat(c2{:})
   result =
        1     2   NaN
        1     2     3