indx <- match(main.df$id, key$id, nomatch = 0) main.df$value[indx != 0] <- key$value[indx]
Sent from my iPad On Mar 21, 2013, at 20:57, Noah Silverman <noahsilver...@ucla.edu> wrote: > Hello, > > I have a large data.frame of 80,000 rows where each row is a record. Each > record is indexed by a unique ID in the first column. > > I need to update values for a column for *some* of the records. I was given > a data.frame with about 10,000 rows and two columns. The first is the record > ID, the second is the new values. > > The slow way to do this is to loop through the new data (10,000 rows) and > update the value in the corresponding master data.frame. However this will > be painfully slow. > > Does anyone have a clever way to shortcut the process. In English, what I > want to do is, "For each row in the update list, lookup the corresponding ID > in the master data frame and update the value." > > > Ideas? > > > -- > Noah Silverman, M.S. > UCLA Department of Statistics > 8117 Math Sciences Building > Los Angeles, CA 90095 > > ______________________________________________ > 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. ______________________________________________ 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.
