Hi Karean, If your first object is called obj1 and the second called obj2, then:
> merge(obj1, obj2, all.x=TRUE) id trait1 trait2 1 1 10.2 9.8 2 2 11.1 10.8 3 3 9.7 NA 4 6 10.2 10.1 5 7 8.9 NA 6 10 9.7 NA 7 11 10.2 NA Hope this helps, Adrian On Wednesday 13 January 2010, karena wrote: > hi, I have a question about merging two files. > For example, I have two files, the first file is like the following: > > id trait1 > 1 10.2 > 2 11.1 > 3 9.7 > 6 10.2 > 7 8.9 > 10 9.7 > 11 10.2 > > The second file is like the following: > id trait2 > 1 9.8 > 2 10.8 > 4 7.8 > 5 9.8 > 6 10.1 > 12 10.2 > 13 10.1 > > now I want to merge the two files by the variable "id", I only want to keep > the "id"s which show up in the first file. Even the "id" does not show up > in the second file, it doesn't matter, I can keep the missing values. So > my question is: how can I merge the two files and keep only the rows whose > "id" show up in the first file? > I know how to do it is SAS, just use the following code: > merge data1(in=in1) data2(in=in2); > by id; > if in1; > > but I really have no idea about how to do it in R. > > thank you in advance, > > karean > -- Adrian Dusa Romanian Social Data Archive 1, Schitu Magureanu Bd. 050025 Bucharest sector 5 Romania Tel.:+40 21 3126618 \ +40 21 3120210 / int.101 Fax: +40 21 3158391 ______________________________________________ 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.