Thank you for interesting examples. I would find useful to document this behavior also in `?mean`, while `+` operator is also affected, the `sum` function is not. For mean, NA / NaN could be handled in loop in summary.c. I assume that performance penalty of fix is the reason why this inconsistency still exists. Jan
On Mon, Jul 2, 2018 at 8:28 PM, Barry Rowlingson < b.rowling...@lancaster.ac.uk> wrote: > And for a starker example of this (documented) inconsistency, > arithmetic addition is not commutative: > > > NA + NaN > [1] NA > > NaN + NA > [1] NaN > > > > On Mon, Jul 2, 2018 at 5:32 PM, Duncan Murdoch <murdoch.dun...@gmail.com> > wrote: > > On 02/07/2018 11:25 AM, Jan Gorecki wrote: > >> Hi, > >> base::mean is not consistent in terms of handling NA/NaN. > >> Mean should not depend on order of its arguments while currently it is. > > > > The result of mean() can depend on the order even with regular numbers. > > For example, > > > > > x <- rep(c(1, 10^(-15)), 1000000) > > > mean(sort(x)) - 0.5 > > [1] 5.551115e-16 > > > mean(rev(sort(x))) - 0.5 > > [1] 0 > > > > > >> > >> mean(c(NA, NaN)) > >> #[1] NA > >> mean(c(NaN, NA)) > >> #[1] NaN > >> > >> I created issue so in case of no replies here status of it can be > looked up > >> at: > >> https://bugs.r-project.org/bugzilla/show_bug.cgi?id=17441 > > > > The help page for ?NaN says, > > > > "Computations involving NaN will return NaN or perhaps NA: which of > > those two is not guaranteed and may depend on the R platform (since > > compilers may re-order computations)." > > > > And ?NA says, > > > > "Numerical computations using NA will normally result in NA: a possible > > exception is where NaN is also involved, in which case either might > > result (which may depend on the R platform). " > > > > So I doubt if this inconsistency will be fixed. > > > > Duncan Murdoch > > > >> > >> Best, > >> Jan > >> > >> [[alternative HTML version deleted]] > >> > >> ______________________________________________ > >> R-devel@r-project.org mailing list > >> https://stat.ethz.ch/mailman/listinfo/r-devel > >> > > > > ______________________________________________ > > R-devel@r-project.org mailing list > > https://stat.ethz.ch/mailman/listinfo/r-devel > [[alternative HTML version deleted]] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
