[Rd] range() for Date and POSIXct could respect `finite = TRUE`
Martin Maechler
m@ech|er @end|ng |rom @t@t@m@th@ethz@ch
Sat Apr 29 22:47:28 CEST 2023
>>>>> Davis Vaughan via R-devel
>>>>> on Fri, 28 Apr 2023 11:12:27 -0400 writes:
> Hi all,
> I noticed that `range.default()` has a nice `finite =
> TRUE` argument, but it doesn't actually apply to Date or
> POSIXct due to how `is.numeric()` works.
Well, I think it would / should never apply:
range() belongs to the "Summary" group generics (as min, max, ...)
and there *are* Summary.Date() and Summary.POSIX{c,l}t() methods.
Without checking further for now, I think you are indirectly
suggesting to enhance these three Summary.*() methods so they do
obey 'finite = TRUE' .
I think I agree they should.
Martin
> ``` x <- .Date(c(0, Inf, 1, 2, Inf)) x #> [1] "1970-01-01"
> "Inf" "1970-01-02" "1970-01-03" "Inf"
> # Darn! range(x, finite = TRUE) #> [1] "1970-01-01" "Inf"
> # What I want .Date(range(unclass(x), finite = TRUE)) #>
> [1] "1970-01-01" "1970-01-03" ```
> I think `finite = TRUE` would be pretty nice for Dates in
> particular.
> As a motivating example, sometimes you have ranges of
> dates represented by start/end pairs. It is fairly natural
> to represent an event that hasn't ended yet with an
> infinite date. If you need to then compute a sequence of
> dates spanning the full range of the start/end pairs, it
> would be nice to be able to use `range(finite = TRUE)` to
> do so:
> ``` start <- as.Date(c("2019-01-05", "2019-01-10",
> "2019-01-11", "2019-01-14")) end <-
> as.Date(c("2019-01-07", NA, "2019-01-14", NA))
> end[is.na(end)] <- Inf
> # `end = Inf` means that the event hasn't "ended" yet
> data.frame(start, end) #> start end #> 1 2019-01-05
> 2019-01-07 #> 2 2019-01-10 Inf #> 3 2019-01-11 2019-01-14
> #> 4 2019-01-14 Inf
> # Create a full sequence along all days in start/end range
> <- .Date(range(unclass(c(start, end)), finite = TRUE))
> seq(range[1], range[2], by = 1) #> [1] "2019-01-05"
> "2019-01-06" "2019-01-07" "2019-01-08" "2019-01-09" #> [6]
> "2019-01-10" "2019-01-11" "2019-01-12" "2019-01-13"
> "2019-01-14" ```
> It seems like one option is to create a `range.Date()`
> method that unclasses, forwards the arguments on to a
> second call to `range()`, and then reclasses?
> ``` range.Date <- function(x, ..., na.rm = FALSE, finite =
> FALSE) { .Date(range(unclass(x), na.rm = na.rm, finite =
> finite), oldClass(x)) } ```
> This is similar to how `rep.Date()` works.
> Thanks, Davis Vaughan
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