[Rd] range() for Date and POSIXct could respect `finite = TRUE`
Bill Dunlap
w||||@mwdun|@p @end|ng |rom gm@||@com
Thu May 11 19:42:48 CEST 2023
> What do others think?
I can imagine a class, "TemperatureKelvins", that wraps a double but would
have a range of 0 to Inf or one called "GymnasticsScore" with a range of 0
to 10. For those sorts of things it would be nice to have a generic that
gave the possible min and max for the class instead of one that just said
they were -Inf and Inf or not.
-Bill
On Thu, May 11, 2023 at 1:49 AM Martin Maechler <maechler using stat.math.ethz.ch>
wrote:
> >>>>> Davis Vaughan
> >>>>> on Tue, 9 May 2023 09:49:41 -0400 writes:
>
> > It seems like the main problem is that `is.numeric(x)`
> > isn't fully indicative of whether or not `is.finite(x)`
> > makes sense for `x` (i.e. Date isn't numeric but does
> > allow infinite dates).
>
> > So I could also imagine a new `allows.infinite()` S3
> > generic that would return a single TRUE/FALSE for whether
> > or not the type allows infinite values, this would also be
> > indicative of whether or not `is.finite()` and
> > `is.infinite()` make sense on that type. I imagine it
> > being used like:
>
> > ```
> > allows.infinite <- function(x) {
> > UseMethod("allows.infinite")
> > }
> > allows.infinite.default <- function(x) {
> > is.numeric(x) # For backwards compatibility, maybe? Not sure.
> > }
> > allows.infinite.Date <- function(x) {
> > TRUE
> > }
> > allows.infinite.POSIXct <- function(x) {
> > TRUE
> > }
> >
> > range.default <- function (..., na.rm = FALSE, finite = FALSE) {
> > x <- c(..., recursive = TRUE)
> > if (allows.infinite(x)) { # changed from `is.numeric()`
> > if (finite)
> > x <- x[is.finite(x)]
> > else if (na.rm)
> > x <- x[!is.na(x)]
> > c(min(x), max(x))
> > }
> > else {
> > if (finite)
> > na.rm <- TRUE
> > c(min(x, na.rm = na.rm), max(x, na.rm = na.rm))
> > }
> > }
> > ```
>
> > It could allow other R developers to also use the pattern of:
>
> > ```
> > if (allows.infinite(x)) {
> > # conditionally do stuff with is.infinite(x)
> > }
> > ```
>
> > and that seems like it could be rather nice.
>
> > It would avoid the need for `range.Date()` and `range.POSIXct()`
> methods too.
>
> > -Davis
>
> That *is* an interesting alternative perspective ...
> sent just about before I was going to commit my proposal (incl
> new help page entries, regr.tests ..).
>
> So we would introduce a new generic allows.infinite() {or
> better name?, allowsInf, ..} with the defined semantic that
>
> allows.infinite(x) for a vector 'x' gives a logical "scalar",
> TRUE iff it is known that is.finite(x) "makes sense" and
> returns a logical vector of length length(x) .. which is TRUE
> where x[i] is not NA/NaN/+Inf/-Inf .. *and*
> is.infinite := Negate(is.finite) {or vice versa if you prefer}.
>
> I agree that this may be useful somewhat more generally than
> just for range() methods.
>
> What do others think?
>
> Martin
>
>
> > On Thu, May 4, 2023 at 5:29 AM Martin Maechler
> > <maechler using stat.math.ethz.ch> wrote:
> [......]
>
> >> >>>>> Davis Vaughan
> >> >>>>> on Mon, 1 May 2023 08:46:33 -0400 writes:
> >>
> >> > Martin,
> >> > Yes, I missed that those have `Summary.*` methods, thanks!
> >>
> >> > Tweaking those to respect `finite = TRUE` sounds great. It seems
> like
> >> > it might be a little tricky since the Summary methods call
> >> > `NextMethod()`, and `range.default()` uses `is.numeric()` to
> determine
> >> > whether or not to apply `finite`. Because `is.numeric.Date()` is
> >> > defined, that always returns `FALSE` for Dates (and POSIXt).
> Because
> >> > of that, it may still be easier to just write a specific
> >> > `range.Date()` method, but I'm not sure.
> >>
> >> > -Davis
> >>
> >> I've looked more closely now, and indeed,
> >> range() is the only function in the Summary group
> >> where (only) the default method has a 'finite' argument.
> >> which strikes me as somewhat asymmetric / inconsequential, as
> >> after all, range(.) := c(min(.), max(.)) ,
> >> but min() and max() do not obey an finite=TRUE setting, note
> >>
> >> > min(c(-Inf,3:5), finite=TRUE)
> >> Error: attempt to use zero-length variable name
> >>
> >> where the error message also is not particularly friendly
> >> and of course has nothing to with 'finite' :
> >>
> >> > max(1:4, foo="bar")
> >> Error: attempt to use zero-length variable name
> >> >
> >>
> >> ... but that is diverting; coming back to the topic: Given
> >> that 'finite' only applies to range() {and there is just a
> convenience},
> >> I do agree that from my own work & support to make `Date` and
> >> `POSIX(c)t` behave more number-like, it would be "nice" to have
> >> range() obey a `finite=TRUE` also for these.
> >>
> >> OTOH, there are quite a few other 'number-like' thingies for
> >> which I would then like to have range(*, finite=TRUE) work,
> >> e.g., "mpfr" (package {Rmpfr}) or "bigz" {gmp} numbers, numeric
> >> sparse matrices, ...
> >>
> >> To keep such methods all internally consistent with
> >> range.default(), I could envision something like this
> >>
> >>
> >> .rangeNum <- function(..., na.rm = FALSE, finite = FALSE, isNumeric)
> >> {
> >> x <- c(..., recursive = TRUE)
> >> if(isNumeric(x)) {
> >> if(finite) x <- x[is.finite(x)]
> >> else if(na.rm) x <- x[!is.na(x)]
> >> c(min(x), max(x))
> >> } else {
> >> if(finite) na.rm <- TRUE
> >> c(min(x, na.rm=na.rm), max(x, na.rm=na.rm))
> >> }
> >> }
> >>
> >> range.default <- function(..., na.rm = FALSE, finite = FALSE)
> >> .rangeNum(..., na.rm=na.rm, finite=finite, isNumeric = is.numeric)
> >>
> >> range.POSIXct <- range.Date <- function(..., na.rm = FALSE, finite
> = FALSE)
> >> .rangeNum(..., na.rm=na.rm, finite=finite, isNumeric =
> function(.)TRUE)
> >>
> >>
> >>
> >> which would also provide .rangeNum() to be used by implementors
> >> of other numeric-like classes to provide their own range()
> >> method as a 1-liner *and* be future-consistent with the default
> method..
> >>
> >>
> >>
> >>
> >> > On Sat, Apr 29, 2023 at 4:47 PM Martin Maechler
> >> > <maechler using stat.math.ethz.ch> wrote:
> >> >>
> >> >> >>>>> 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
> >> >>
> >> >> > ______________________________________________
> >> >> > R-devel using r-project.org mailing list
> >> >> > https://stat.ethz.ch/mailman/listinfo/r-devel
>
> ______________________________________________
> R-devel using r-project.org mailing list
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