Conditional Counting in Mathematica

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Published on 2011-06-24T19:38:22Z Indexed on 2011/06/25 8:22 UTC
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Considering the following list :

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

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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}}

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

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