Group cell-array row by an ID in another row

Question

I have got this cell-array:

QueueArr = ...
{   [1]    [5]    [1]    [2]    [1]    [ 1]    [ 5]    [ 1]    [ 2] ;  
    [6]    [8]    [7]    [9]    [5]    [10]    [18]    [17]    [19] }

Now I want to group the second row depending on the first one. My result cell-array should look like this:

loopCell = ...
{    [          1]    [          2]    [          5] ;
     [6 7 5 10 17]    [       9 19]    [       8 18] }

I solved this problem with this code:

%// convert from cell to a matrix
loopMatrix = cell2mat(QueueArr);
%// get the unique elements from the first row
loopMatrixUnique = unique(loopMatrix(1,:));
%// create the result cell
loopCell = cell(2,size(loopMatrixUnique,2));
%// iterate through the unique indexes
for i = 1:size(loopMatrixUnique,2)
    %// saving the first row
    loopCell{1,i} = loopMatrixUnique(i);
    %// calculating the grouped elements
    loopCell{2,i} = loopMatrix(2,loopMatrix(1,:) == loopMatrixUnique(i));
end

My question now is whether there is an easier or more ideal solution to my problem.

Answer 1

I solved it myself with accumarray. thx to @Dan for the hint.

%// save the second row
sections = [QueueArr{2,:}];

%// get unique chapters and subs
[chapters, ~, subs] = unique([QueueArr{1,:}]);

%// create the grouped cell-array 
groups = accumarray(subs, sections, [], @(x) {x});

%// create the result cell-array
loopCell = [num2cell(chatpers); groups.'];