Help with knnsearch searching through mirrored ghost particles.

I've attached the necessary workspace to recreate what I have tried to do. Essentially, I am trying to print the particle ID's and distances of their nearest neighbors ( up to 20 right now, that's what 'res' is), with the search INCLUDING ghost particles 4001-8000.

There are 4000 particles and 4000 mirrors, and the position (x,y) values for those 1-4000 are written to 'Y' ; then those values are mirrored over the x axis to create axi-symmetric tracers for a proto neutron star, and those mirror particles are written to 'X' (ID # 4001-8000).

I thought that by using 'full' - the concatenated group of all 8000 particles - in the knnsearch call that it would do what I want it to do: search across the pole (x axis) for neighbors as well, not just along the rays the particles belong to. Along one ray, the particle ID's will be multiples of 40, i.e. 1, 41, 81, 121, ... etc are in the same ray.

However, it's not, it simply moves along the ray and then eventually jumps to the rays beside of it. I'm going to include the output IDX before and separate from the code, which is the output for the ID's for all particles up to their 20th closest neighbor, so you can see which particles it chooses. Just for clarity, though, I don't want the neighbor ID's of all 8000. Just the 4000 regular particles, because if it works correctly, the neighbors should be the same for mirrors, i.e. particle 1 and particle 4001 should have the same neighbors because they are mirrors of each other.

      val(:,:,1) =

        Columns 1 through 18

           1    41    81   121   161   201   241   281   321   361   401   441   481   521   561     2    42   601

        Columns 19 through 20

          82   122

      val(:,:,2) =

        Columns 1 through 18

           1    41    81   121   161   201   241   281   321   361   401   441   481   521   561     2    42    82

      ...

      val(:,:,3999) =

        Columns 1 through 9

              3680        3720        3640        3760        3600        3800        3560        3840        3520

        Columns 10 through 18

              3880        3480        3440        3920        3400        3960        3360        3320        4000

        Columns 19 through 20

              3280        3240

      val(:,:,4000) =

        Columns 1 through 9

              3840        3880        3800        3920        3760        3960        3720        3680        4000

        Columns 10 through 18

              3640        3600        3560        3520        3480        3440        3400        3360        3320

        Columns 19 through 20

              3280        3240

--------------------------------------------------------------------------------------------------------

    function [IDX, D] = neighborsearch(MdlKD,X,Y, k, res)

                                                     %The IDX and Distance matrices are initialized

        IDX (1, 1:res, 1:4000) = 0;
        D (1, 1:res, 1:4000) = 0;

       full = [Y;X];
                                                    % For-loop through REGULAR particles (1-4000) and 
                                                    %outputs distances and ID's of neighbors %
            for i=1:size(Y, 1)

                [IDX2, D2] = knnsearch(MdlKD,full(i,:),'k', res);              %Selecting neighbors from all particles, 
                                                                               % Including ghosts (4001-8000)

                 IDX(:,:,i) = IDX2;                                             % Adding to the existing matrices
                 D(:,:,i) = D2;

            %display the loop iteration number and time %
            fprintf('\tLoop: %4d at %4d-%02d-%02d %02d:%02d:%06.3f\n', i, datevec(now))
            end
    end