Thanks, now I understand what's happening. Maybe a line explaining this could be added to the help text for mean?
Pascal Niklaus On Wed 07-Jan-2009 13:29:25 Prof Brian Ripley wrote: > Pascal A. Niklaus wrote: > > Hi all, > > > > I ran into a problem in some of my code that could be traced back to > > 'mean' > > > > sometimes returning NA and sometimes NaN, depending on the value of na.rm: > >> mean(c()) > > > > [1] NA > > > >> mean(c(NA),na.rm=T) > > > > [1] NaN > > > > However, I don't understand the reasoning behind this and would > > appreciate and explanation. > > > > I understand that the mean of an empty vector is not definied, > > Not so, it is well-defined as 0/0 = NaN. > > > but I don't > > understand why it matters whether the vector was empty from the beginning > > You didn't try that case: mean(numeric(0)) is also NaN. The issue is that > > > typeof(c()) > > [1] "NULL" > > is not numeric (not evan a vector), and so mean() of it is undefined. > > > or only after removing the NAs. > > Speculation (and wrong). > > > Pascal Niklaus > > > > ______________________________________________ > > 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.
