MATLAB: Shuffling elements within the rows of a matrix

matrix elementsrandomlyshuffleshuffle within rows

Say I have a matrix, I would like to shuffle the elements within the rows randomly. For example,
A = randi(1000, 3,4)
A =
   815   279   958   793
   906   547   486   960
   127   958   801   656
I need to get the shuffled matrix like this
B =
   279   793   958   815
   960   547   486   906
   801   127   958   656
The most straightforward way I can think of achieving this is to use randperm to shuffle the indices of each row, and then loop over the number of rows to create the shuffled matrix. But I would like to get it all done in one go, preferably more elegantly than using a loop, because I need to do this for large matrices many times. So, alternatively, I tried this:
[nr,nc] = size(A);
P=perms(1:nc);
col_indx_mtrx = P(randi(size(P,1),nr,1),:);
ri = repmat((1:nr)',1,nc);
which gives me
ri =
       1     1     1     1
       2     2     2     2
       3     3     3     3
col_indx_mtrx =
       2     1     4     3
       3     4     1     2
       1     4     2     3
Now, after this, I thought if I simply do
B = A(ri,col_indx_mtrx)
I am done. But, I don't get the desired result, because when I give the row and column indices as matrices, MATLAB tries to create a matrix with all combinations of the row and column indices?
Essentially, what I need is to create the shuffled matrix B such that
B(1,1) = A(ri(1,1), col_indx_mtrx(1,1))
and so on. Is there an elegant way to achieve this last step? I tried to use arrayfun, but I could not get it done.
Or, better, is there a more elegant way of achieving the overall objective?
Any help would be greatly appreciated.

Best Answer

Here's one way:
% Original matrix
A = randi(1000, 3,4);
[M,N] = size(A);
% Preserve the row indices
rowIndex = repmat((1:M)',[1 N]);
% Get randomized column indices by sorting a second random array
[~,randomizedColIndex] = sort(rand(M,N),2);
% Need to use linear indexing to create B
newLinearIndex = sub2ind([M,N],rowIndex,randomizedColIndex);
B = A(newLinearIndex);
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