Creating a Combination of Multiple Arrays

I'm having trouble coming up with code to create a combination between two arrays. In my first array, result, I computed the Cartesian product between the two vectors of A.

>> A = {[1 2 3], [4 5 6]}
   c = cell(1,numel(A));
   [c{:}] = ndgrid(A{:});
   result = cell2mat(cellfun(@(v)v(:), c, 'UniformOutput', false) )

resulta =

       1     4
       2     4
       3     4
       1     5
       2     5
       3     5
       1     6
       2     6
       3     6

My second array is:

resultb =

       1     3
       2     4

I am trying to create iterations between the rows of result and result b. To make it clearer, I want my output array to look like this:

 resultc=

     1     4     1     3
     2     4     1     3
     3     4     1     3
     1     5     1     3
     2     5     1     3
     3     5     1     3
     1     6     1     3
     2     6     1     3
     3     6     1     3
     1     4     2     4
     2     4     2     4
     3     4     2     4
     1     5     2     4
     2     5     2     4
     3     5     2     4
     1     6     2     4
     2     6     2     4
     3     6     2     4

How would I create code to achieve this regardless of the sizes of matrices resulta and resultb? Thanks!

Answer 1

[OCDER]

combvec(resulta', resultb')'

[Rachel Anthony]

Thanks for your answer! Would there be a way to do this if result a and result b were cell arrays instead? I'm switching the vectors to cell arrays so they can hold strings, but I want the functionality to stay the same. Thank you again!

[OCDER]

I don't know a more direct way off the top of my head, but you could make a combination of indices of the cell arrays instead, and then assemble your combination cell array at the way end. See this example:

resulta = [
       1     4
       2     4
       3     4
       1     5
       2     5
       3     5
       1     6
       2     6
       3     6];

resultb =[
       1     3
       2     4];      

%Just making some example cell arrays
cella = num2cell(resulta);
cella{1} = 'a';
cellb = num2cell(resultb);
cellb{2} = 'b';

%1) create a joined matrix of size (Ma+Mb)x1
cellab = [cella(:); cellb(:)];

%2) find all combination of the linear indices of cella and cellb
IdxA = reshape(1:numel(cella), size(cella));
IdxB = reshape(1:numel(cellb), size(cellb)) + numel(cella); %Add numel(cella) at end because you want the linear index of cellab
ComboIdx = combvec(IdxA', IdxB')';

%3) now make your combination cell array
ComboCell = reshape(cellab(ComboIdx(:)), size(ComboIdx));

[Rachel Anthony]

That works, thank you so much!

Answer 2

[Matt J]

For those without the Neural Network Toolbox,

resultb=[1 3; 2 4];

A = {[1 2 3], [4 5 6],1:size(resultb,2)}

N=numel(A)-1;

[c{1:N+1}]=ndgrid(A{:});

result=[reshape( cat(N+1,c{1:N})  ,[],N )   ,resultb(c{N+1},:)]