[R] Ids with matching number combinations?

[Marine Andersson]

Hi,

If I have two datasets like this:
df=data.frame("id"=rep(1:10,10, each=10), "item1"=sample(1:20, 100, replace=T)
df2=data.frame("a"=c(8, 8,10,9, 5, 1,2,1), "b"=c(16,18,11, 19,18, 11,17,12))

How do I find out which ids in the df dataset that has a match for both the numbers occuring in the same row in the df2 dataframe? In the output I would like to get the matching id and the rownumber from the df2.

Output something like this
Id                        Rownr
2                         1
5                         1
7                         4

My actual problem is more complex with even more columns to be matched and the datasets are large, hence the solution needs to be efficient.

Kind regards,





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