I found a solution: pairs<-merge(subset(data.frame,cond==2,select=c(group,x),subset(data.frame,cond==3,select=c(group,x)),by=c("group"))
That yields something like group cond.x cond.y A 4 6.5 D 5 6 E 4 6 now I just need to figure out how I embed this into a function together with the test, so that I don't have to write to much .... Stefan Grosse > Dear list, > > I want to extract pairs of values out of a dataframe where one > criteria/condition does match. > > I have an experiment with 3 conditions which were not always applied: > > e.g.: > > group cond x > A 1 2 > A 2 4 > A 3 6.5 > B 1 3 > B 2 4.5 > C 1 2.5 > C 3 4 > D 2 5 > D 3 6 > E 1 1 > E 2 4 > E 3 6 > > > Now I wanted to extract the x of those groups where condition 2 and > condition 3 do both exist. > > In this example that would be groups A, D and E and the extracted pairs > e.g.: > cond2 cond3 > 4 6.5 > 5 6 > 4 6 > > ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.