st: A contingency table of counts by case

[Serguei Kaniovski <kaniovsk@wifo.ac.at>]

I have the following data:

  case id x
1    1  1 1
2    1  2 1
3    1  3 1
4    2  1 1
5    2  2 0
6    2  3 1
7    3  2 1
8    3  3 0
9    3  4 0

"case" - cases, "id" - persons, and "x" - binary state.

I would like to count the number of "cases" in which any two "id"

a. both have "x=1",
b. the first has "x=0" - the second has "x=1",
c. the first has "x=1" - the second has "x=0",
d. both have "x=0",

and transform these counts to relative frequencies in the total number 
of "cases" the pair has been observed together. The composition of 
"case" by "id" varies, e.g. case=1,2 have id=1,2,3, but case=3 has id=2,3,4.

I guess this can be accomplished using nested loops, but do you know of 
a better solution? I have about 20000 observations.

Thanks a lot for you help,
Serguei Kaniovski
--
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Austrian Institute of Economic Research (WIFO)

Name: Serguei Kaniovski			P.O.Box 91
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Mail: Serguei.Kaniovski@wifo.ac.at

http://www.wifo.ac.at/Serguei.Kaniovski

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