Preventing repeated sequences in a matrix

I have a 192 x 3 matrix, order(192 x 3):

order(:, 1) and order(:, 2) both contain repeating values of 1 - 16, and order(:, 3) contains repeating values of 1 and 2. I need to shuffle the matrix, while preventing any repeats of more than three of the same value in the last column, so order(:, 3) should never show more than 3 repeats of 1 or 2.

This is what I have, which worked for a smaller version of the matrix just fine, but seems to get stuck with a slightly larger matrix:

not_good = true;

    while not_good

    not_good = false;

    order = Shuffle(order);

    % returns an array of 1s and 0s indexing the position of the values for 1                                  and 2

    R1 = order(:, 3) == 1;
    R2 = order(:, 3) == 2;

    % checks for repeats, returns 1 if repeats are present

    rep_test1 = any(diff([1; find(R1)])>3);
    rep_test2 = any(diff([1; find(R2)])>3);

    if rep_test1 > 0 || rep_test2 > 0
    not_good = true;
   end
  end

Any comments much appreciated. Thanks.

[Matt Fig]

What is Shuffle?

>> help Shuffle

Shuffle not found.

And give the matrix order. Is this a good approximation of order?

order = cell2mat(arrayfun(@(x) randperm(x).',16*ones(12,2),'Un',0));
order = [order cell2mat(arrayfun(@(x) randperm(x).',2*ones(96,1),'Un',0))];

Answer 1

[Matt Fig]

I think I figured out that Shuffle is on the FEX.

Part of the problem is that you are just going to have more chance to get 3+ of a kind in a row the more numbers you add. This is faster, however. For this order array (or the more structured one I show above), it takes less than a minute.

order = [mod(randperm(192),16);mod(randperm(192),16);...
         mod(randperm(192),2)].'+1;

T = true(1,4);  % 3 in a row is o.k.
while true

     order = Shuffle(order);

     if isempty(strfind(order(:,3).'==2,T))
         if isempty(strfind(order(:,3).'==1,T))
             break
         end
     end
  end

Another note: Your code will let pass an order that has 4 or more in a row as the end of the third column...

[Matt Fig]

I noticed the first code I posted used

T = ones(1,3);

When it should have been

T = ones(1,4);

Now fixed.

[Lauren Shone]

Thank you! This works.

Answer 2

[Jan]

It will be much cheaper to shuffle the index vector only and use an UINT8 as long as less than 255 elements are processed (based on Matt's code):

index = uint8(1):uint8(192);
data  = [mod(randperm(192), 16); mod(randperm(192), 16)].';
crit  = mod(randperm(192), 2) + 1;  % Avoid repeated transposition
T = true(1,4); 
while 1  % Cheaper than the function(!) TRUE
   index = Shuffle(index);
   test  = crit(index);
   if isempty(strfind(test == 2, T))
       if isempty(strfind(test == 1, T))
           break
       end
   end
end
% Create the full data once only after the calculations:
result = cat(2, data(index, :), double(crit(index).'));