Yes. data.df[,wcol,drop=FALSE] For an explanation of drop see ?"[.data.frame"
"Chuck White" <[email protected]> wrote in message news:20100202212800.o8xbu.681696.r...@mp11... > Additional clarification: the problem only comes when you have one column > selected from the original dataframe. You need to make the following > modification to the original example: > > data.df <- data.frame(aa=c(1,1,0), cc=c(1,0,0), aab=c(0,1,0), > aac=c(0,0,1), bb=c(1,0,1)) > > And, the following seems to work: > data.frame(sapply(col2.uniq, function(col) { > wcol <- which(col==col2) > as.numeric(rowSums(data.frame(data.df[,wcol]))>0) > })) > I had to wrap data.df[,wcol] in another data.frame to handle situations > where wcol had one element. Is there a better approach? > > > ---- Chuck White <[email protected]> wrote: >> Hello -- I am trying to merge columns in a dataframe based on substring >> matches in colnames. I would appreciate if somebody can suggest a >> faster/cleaner approach (eg. I would have really liked to avoid the >> if-else piece but rowSums does not like that). Thanks. >> >> data.df <- data.frame(aa=c(1,1,0), bbcc=c(1,0,0), aab=c(0,1,0), >> aac=c(0,0,1), bbk=c(1,0,1)) >> col2 <- substr(colnames(data.df),1,2) >> >> col2.uniq <- unique(col2) >> names(col2.uniq) <- col2.uniq >> >> data.frame(sapply(col2.uniq, function(col) { >> wcol <- which(col==col2) >> if(length(wcol)>1) { >> tmp <- rowSums(data.df[,wcol]) >> } else { >> tmp <- data.df[,wcol] >> } >> as.numeric(tmp>0) >> })) > ______________________________________________ [email protected] 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.
