Thanks-- that works for what I'm trying to do. I was also wondering, in the data frame example you gave, if I just wanted to get rid of rows where the "a" value is 5, how would I do that? -- View this message in context: http://r.789695.n4.nabble.com/Unique-subsetting-question-tp2550453p2550836.html Sent from the R help mailing list archive at Nabble.com.