quick syntax question for saving run time

I have the following:

          m1 = rand(5,5)
          m2 = rand(5,5)
          m3 = rand(5,5)
          m4 = rand(5,5)
          m3D = cat(3, m1, m2, m3, m4);
          % Find the min and a map of what matrix it occurred in.
          [min2DImage matrixWhereItOccurs] = min(m3D, [], 3)

Now I would like to have accumlation array where I update that array by adding one to the 3rd dimension with index referenced from matrixWhereItOccurs

      sz = sz(m3D);
      accum_arr = zeros(sz(1),sz(2),sz(3)

Let's say matrixWhereItOccurs(2,3)=4, then accumm_arr(2,3,4)=accum_arr(2,3,4)+1; I want to do this for ALL elements now without going into loop as in my work the arrays are huge.Could you please help? Thanks

[per isakson]

Please format to save my time :)

[jenka]

sorry.here it is.

Answer 1

[Honglei Chen]

ind = sub2ind(sz,repmat((1:sz(1))',1,sz(2)),repmat(1:sz(2),sz(1),1),...
       matrixWhereItOccurs);
accum_arr(ind(:)) = accum_arr(ind(:))+1;