I expect DT2 <- unique.data.frame(DT1) to be a new object, but get a warning about pointers, so apparently it is not...?
A short example: DT1 <- data.table(1) DT2 <- unique.data.frame(DT1) DT2[,gah:=1] An example closer to my application, undoing a cartesian/cross join: DT1 <- CJ(A=0:1,B=1:6,D0=0:1,D=0:1)[D>=D0] setkey(DT1,A) DT2 <- unique.data.frame(DT1[,-which(names(DT1)%in%'B'),with=FALSE]) DT2[,gah:=1] # warning: I should have made a copy, apparently I'm fine with explicitly making a copy, of course, and don't really know anything about pointers. I just thought I'd bring it up. --Frank
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