# it's not clear what your question is, but here's a stab in the dark at a solution!
ind<- !is.na(dataframe$A) & !is.na(dataframe$B) dataframe$A[ind] + dataframe$B[ind] - Dan P.S. I'm sure there are ways to do this using one of R's functions for automatically removing NA's (na.rm = T), but unless you use them all the time, their behavior is not always predictable (e.g., sometimes it ignores a whole row with one NA in it; sometimes it treats NAs as zeros). Explicitly defining the indices that you want to exclude may make it easier to avoid difficult-to-find errors. -- View this message in context: http://r.789695.n4.nabble.com/Handling-NA-in-summation-tp4711923p4711932.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
