Try this. It uses the fact that 2 column matrices can be used as subscripts (as described in the Matrices and arrays section of ?Extract):
with(recodes, replace(as.matrix(main), cbind(id, qst + 1), value)) It returns a matrix so use as.data.frame on that to turn it back to a data frame, if need be. On Mon, Mar 17, 2008 at 9:10 PM, Andrew C. Ward <[EMAIL PROTECTED]> wrote: > Dear list, > > I'd like to update certain rows/columns in a data > frame with new values. The application is that > survey respondents may give an answer of "Other" > to a categorical question and then provide some > text describing what they mean. This text is then > reviewed and placed into a category. These edits > or recodes then need to be merged back into the > main dataset. > > A small example follows. > > # Generate a main data set (10 people, 2 questions) > main <- data.frame(id=1:10, q1=sample(1:5, size=10, > replace=TRUE), q2=sample(1:5, > size=10, replace=TRUE)) > # Generate a corresponding recodes dataset > recodes <- reshape(main, idvar="id", direction="long", > varying=list(2:3), v.names="value", > timevar="qst") > recodes <- recodes[sample(seq(nrow(recodes)), 10, > replace=FALSE),] > recodes$value <- recodes$value + sign(runif(1)-0.5) > > I could easily use a for() loop to update the main > dataset. The recodes dataset can get quite large, > however, so I would rather avoid this. > > The question: > Is there some efficient way, using apply() perhaps, > that I can update the main dataset with the new > values from the recodes dataset? > > Thanks very much for your advice! > > Regards, > > Andrew C. Ward > > CAPE Centre > Department of Chemical Engineering > The University of Queensland > Brisbane Qld 4072 Australia > > ______________________________________________ > 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.
