Hi > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Cesar Terrer > Sent: Friday, March 01, 2013 4:21 AM > To: r-help@r-project.org > Subject: [R] Select first element of each factor and convert to NA > > Hi all, > > > > I have a dataframe of the following type: > > > > Day Place dendrometer max > > 1 1 1 4684 > > 2 1 1 4831 > > .. > > 1 1 2 2486 > > 2 1 2 2596 > > . > > 1 2 1 6987 > > 2 2 1 6824 > > > > I need the first element of each dendrometer as NA, so every time R > calculates "max" for a new dendrometer (independently of the place), > starts with NA, like this: > > > > Day Place dendrometer max > > 1 1 1 NA > > 2 1 1 4831 > > .. > > 1 1 2 NA > > 2 1 2 2596 > > . > > 1 2 1 NA > > 2 2 1 6824 >
Just as a curiosity, do you want to change max value for a Day 1 to NA? If yes, DF$max[DF$Day==1] <- NA shall work. > > > Could you also let me know I could calculate MEAN of the max column for > each dendrometer within each ring (sapply, aggregate?) instead of > calculating mean for the entire max column? ?aggregate or maybe ?ave Regards Petr > > > > Thanks! > > > > > [[alternative HTML version deleted]] > > ______________________________________________ > 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.
