Dear Bill, Thanks a lot this is what I was looking for.
Emmanuel On 2 November 2016 at 15:59, William Dunlap <wdun...@tibco.com> wrote: > Give your new column a vector type - NULL cannot be extended beyond length > 0. Also, the syntax df$col<-NULL means to remove 'col' from 'df'. > > > df <- data.frame(id=integer(0), data=numeric(0)) > > df$new.col <- character(0) > > str(df) > 'data.frame': 0 obs. of 3 variables: > $ id : int > $ data : num > $ new.col: chr > > (Think of 'zero-row' or 'zero-column' data.frames, not 'empty' > data.frames, which could be either.) > > > > Bill Dunlap > TIBCO Software > wdunlap tibco.com > > On Wed, Nov 2, 2016 at 6:48 AM, Emmanuel Levy <emmanuel.l...@gmail.com> > wrote: > >> Dear All, >> >> This sounds simple but can't figure out a good way to do it. >> >> Let's say that I have an empty data frame "df": >> >> ## creates the df >> df = data.frame( id=1, data=2) >> >> ## empties the df, perhaps there is a more elegant way to create an empty >> df? >> df = df[-c(1),] >> >> > df >> [1] id data >> <0 rows> (or 0-length row.names) >> >> Now, how can I add a third column name to that empty df? >> >> Normally I would use df$new.col = 1 >> >> But here I can't use this because it's empty! >> >> I tried df$new.col=NULL -- this doesn't give an error but doesn't add the >> column. >> >> Thanks for your help, >> >> Emmanuel >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> 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/posti >> ng-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> > > [[alternative HTML version deleted]] ______________________________________________ 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.