Replace duplicated elements with NA, instead of removing them
Solution 1:
You were pretty close. I'm not sure what DFl is though. But this works...
DF <- data.frame(A=c("a", "a", "a", "b", "b", "c"))
DF$A[duplicated(DF$A)] <- NA
> DF
A
1 a
2 <NA>
3 <NA>
4 b
5 <NA>
6 c
Solution 2:
Taking the example from above, if you have a file with several columns, and you want to do the same for each column, you could use this:
DF <- data.frame(col1=c("a","b","a","c","b","c"),col2=c("b","c","c","c","a","a"))
for(i in 1:ncol(DF)){
DF[,i][duplicated(DF[,i])] <- NA
}