Transforming data problem

Hi, All! I have the following problem. Let's suppose I have the following tab-delimited data file: data2.txt: ======= user1 web1 2002-03-25 14:43:17 user1 web2 2002-03-25 14:43:20 user2 web2 2002-03-25 14:50:02 user2 web2 2002-03-25 14:55:00 user1 web1 2002-03-25 14:45:00 user3 web2 2002-03-26 16:20:00 user3 web3 2002-03-26 16:21:17 user4 web1 2002-03-26 18:45:23 user4 web3 2002-03-26 18:50:00 user4 web1 2002-03-26 19:01:00 user4 web2 2002-03-26 19:20:20 Now... I would like to get a matrix where in cells are counts of users which has been on the both websites. Like this: web1 web2 web3 web1 4 2 1 web2 2 4 2 web3 1 2 2 That means: 4 diferent users were on web1 2 users were on web1 AND web2,... and so on. Now... how to do that? There are actually three problems, which are described in http://www.ljudmila.org/matej/count/pajek.phps... the first one is solved, the second and third not... This can be found as second problem. Can anyone help me? Thanks & bye, Matej