Question

Considering the following list :

dalist = {{1, a, 1}, {2, s, 0}, {1, d, 0}, {2, f, 0}, {1, g, 1}}

I would like to count the number of times a certain value in the first column takes a certain value in column 3.

So in this example my desired output would be:

{{1,1,2},
{1,0,1},
{2,1,0},
{2,0,2}}

or :

Where the latest sublist {2,0,2} being read as: When the value is 2 in the first column, a corresponding value (same row in matrices world) in column 3 of 0 is present twice.

I hope this is not to confusing. I added the second Column to convey the fact that the columns are distant to each other.

If possible, no reordering should happen.

EDIT :

{1,2,3,4,5}

{1,0}

are the exact values taken by the columns I am actually dealing with in my data.

I know I am missing the correct description. Please edit if you can and know it. Thank you

Answer 1

I tried to come up with something brand new using Sasha’s assumptions about the required output, but it got more similar to his code than I thought it would be. Still the differences are interesting enough to post.

   {#1, #2, Count[dalist[[All, {1, 3}]], {##}]} & @@@ 
    Tuples[
       {DeleteDuplicates@dalist[[All, 1]], 
        DeleteDuplicates@dalist[[All, 3]]}
    ]

Edit
With your clarification about the input the code can be simplified and actually improved to:

   {#1, #2, Count[dalist[[All, {1, 3}]], {##}]}& @@@Tuples[{Range[5],{0,1}}]

The first version is correct only if at least one example of each possible outcome is actually present in each column.