Hi, If x is a data frame, then x$getmean will try to get the vector named getmean in x. You put "()" after x$getmean. I think r is confused about it. It appears that you want to call a function named getmean(). -- View this message in context: http://r.789695.n4.nabble.com/operator-is-invalid-for-atomic-vectors-tp4703112p4703114.html Sent from the R help mailing list archive at Nabble.com.