Hi list,
is there a package or function to compute the frequencies of pairs of chars in
a variable across a grouping variable? Eg:
d <- data.frame(ID=gl(2,3), F=c("A","B","C","A","C","D"))
> d
ID F
1 1 A
2 1 B
3 1 C
4 2 A
5 2 C
6 2 D
Now I want to summarize the frequencies of all pairs A-B, A-C, A-D, B-C, B-D,
C-D across ID:
A B C D
A - 1 2 1
B - - 1 0
C - - - 1
here, the combination A-C is most frequent. The real problem behind that is
that 'F' codes diagnoses and I search for the most often pairs of diagnoses.
Thanks, Sven
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