On Mon, 2006-08-07 at 14:05 -0600, Mark Na wrote: > Dear R community, > > I have two dataframes "first" and "second" which share a unique identifier. > > I wish to make a new dataframe "third" retaining only the rows in > "first" which also occur in "second". > > I have tried using merge but can't seem to figure it out. Any ideas? > > Thanks! > > Mark
Do you want to actually join (merge) matching rows from 'first' and 'second' into 'third', or just get a subset of the rows from 'first' where there is a matching UniqueID in 'second'? In the first case: third <- merge(first, second, by = "UniqueID") Note that the UniqueID column is quoted. In the second case: third <- subset(first, UniqueID %in% second$UniqueID) See ?merge, ?"%in%" and ?subset HTH, Marc Schwartz ______________________________________________ R-help@stat.math.ethz.ch 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.
