Creating a 3D frequency (histogram/bar graph)

If I had 4 3x3 lower triangular matrices like:

    A = [5     0     0
         1     3     0
         5     5     5]

    B = [4     0     0
         5     5     0
         4     5     4]

    C = [2     0     0
         4     1     0
         1     2     5]

    D = [4     0     0
         2     3     0
         5     2     1]

I would like to keep track of the frequency of a number occurring in each spot of the matrix. In some sense, I would like to create a matrix whose values are actually vectors. For the example above, if I had a matrix, M, that counted the frequency, then:

   M(1,1) = [0 0 1 0 2 1] % assuming I start the count 0 and only consider the lower triangle
   M(2,1) = [0 1 1 0 1 1]
   M(2,2) = [0 1 0 2 0 1]

... and so on.

After that, I would like to create a 3D plot with x-axis being the column position, y-axis being the count (from 0 to 5), and the z-axis keeps track of the frequencies.

Thanks!