[R] A contingency table of counts by case

[Jacques VESLOT]

library(gtools)
apply(combinations(9,2), 1, function(x) with(df[df$id %in% x, ], table(x, id)))
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Jacques VESLOT

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Serguei Kaniovski a écrit :
> Here is an example of the data.frame that I have,
> 
> df<-data.frame("case"=rep(1:5,each=9),"id"=rep(1:9,times=5),"x"=round(runif(length(rep(1:5,each=9)))))
> 
> "case" represents the cases,
> "id" the persons, and
> "x" is the binary state.
> 
> I would like to know in how many cases any two persons
> 
> a. both have "1",
> b. the first has "0" - the second has "1",
> c. the first has "0" - the second has "0",
> d. both have "0".
> 
> There will be choose(9,2) sums, denoted s_ij for 1<=i<j<=9,
> where i and j are running indices for an "id"-pair.
> 
> Please help, this is way beyond my knowledge of R!
> 
> Thank you,
> Serguei Kaniovski