On Wed, Oct 21, 2015 at 4:57 PM, Hadley Wickham <h.wick...@gmail.com> wrote: > x <- as.Date(Inf, origin = "1970-01-01") > x > #> [1] NA > str(x) > #> Date[1:1], format: NA > unclass(x) > #> [1] Inf > > It's not clear what the correct behaviour is. The documentation for > ?Date has: "It is intended that the date should be an integer,", which > suggests that -Inf and Inf are not valid dates. But if that's true the
You omitted the second half of the sentence, which contains important information. The entire sentence is, "It is intended that the date should be an integer, but this is not enforced in the internal representation." Since it's not enforced internally, it doesn't necessarily follow that non-integer values are invalid dates. The rest of the paragraph describes how fractional (internal) dates can be created. Both ?format.Date and ?strptime say that 'NA' dates/times are printed as NA_character_. It might be clearer to say that "invalid" dates/times are printed as NA_character_. > behaviour for max.Date() needs some thought: > > max(as.Date(NA), na.rm = TRUE) > #> Warning in max.default(structure(NA_real_, class = "Date"), na.rm = TRUE): > #> no non-missing arguments to max; returning -Inf > #> [1] NA > > If dates are integers, then there is no date that is smaller than all > other dates, so it's not clear what max() should return - NA? > But they're not integers in the strict sense. > Hadley > > -- > http://had.co.nz/ > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel -- Joshua Ulrich | about.me/joshuaulrich FOSS Trading | www.fosstrading.com ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
