Thank you dear friends. You have cleared my first doubt.  My second doubt: I have the same data sets "Elder" and "Younger". Elder <- data.frame(  ID=c("ID1","ID2","ID3"),  age=c(38,35,31)) Younger <- data.frame(  ID=c("ID4","ID5","ID3"),  age=c(29,21,"NA"))
 Row ID3 comes in both data set. It has a value (31) in "Elder" while "NA" in "Younger". I need output like this. ID   age ID1 38 ID2 35 ID3 31 ID4 29 ID5 21 Kindly help me. On Thursday, 16 January 2014 9:16 PM, Marc Schwartz-3 [via R] <ml-node+s789695n4683682...@n4.nabble.com> wrote:  Not quite: > rbind(Elder, Younger)   ID age 1 ID1  38 2 ID2  35 3 ID3  31 4 ID4  29 5 ID5  21 6 ID3  31 Note that ID3 is duplicated. Should be: > merge(Elder, Younger, by = c("ID", "age"), all = TRUE)   ID age 1 ID1  38 2 ID2  35 3 ID3  31 4 ID4  29 5 ID5  21 He wants to do a join on both "ID" and "age" to avoid duplications of rows when the same ID and age occur in both data frames. If the same column names (eg "Var") appears in both data frames and are not part of the 'by' argument, you end up with Var.x and Var.y in the result. In the case of two occurrences of the same ID but two different ages, if that is possible, both rows would be added to the result using the above code. Regards, Marc Schwartz On Jan 16, 2014, at 9:04 AM, Frede Aakmann Tøgersen <[hidden email]> wrote: ________________________________ ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. ________________________________ If you reply to this email, your message will be added to the discussion below: http://r.789695.n4.nabble.com/Doubt-in-simple-merge-tp4683671p4683682.html To start a new topic under R help, email ml-node+s789695n78969...@n4.nabble.com To unsubscribe from R help, click here. NAML -- View this message in context: http://r.789695.n4.nabble.com/Doubt-in-simple-merge-tp4683671p4683718.html Sent from the R help mailing list archive at Nabble.com. [[alternative HTML version deleted]]
______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.