Hi, If I understand it correctly, you could use ?unique() or ?duplicated() ?unique(mydf) #or mydf[!duplicated(mydf),] A.K. Hello everyone. I am very new to R and very bad in programming. I need to remove some rows based on multiple conditions. For example, I have this table: Id = c(1,1,2,2,3,3) url = c("a", "b", "a", "a", "b","b") mydf = data.frame(Id,url) I want to remove the second row of url of the same Id, but keep both rows of url if they are different. Thank you very much.