[Rd] range() for Date and POSIXct could respect `finite = TRUE`

Martin Maechler m@ech|er @end|ng |rom @t@t@m@th@ethz@ch
Mon May 22 11:20:36 CEST 2023


>>>>> Gabriel Becker 
>>>>>     on Fri, 19 May 2023 09:23:50 -0700 writes:

    > Hi All,

    > I think there may be some possible confusion about what allowsInf would be
    > reporting (or maybe its just me :) ) if we did this.

    > Consider a class "myclass", S3, for starters,

    > with

    > setMethod("allowsInf", "myclass", function(obj) FALSE)

    > Then, what would

    >   myclassthing <- structure(1.5, class = "mything")
    >   myclassthing[1] <- Inf

    > do. 

Hmm.. You can always define classes and methods which jointly are
complete non-sense; e.g., people have also defined classes with a
length() method that returned a result of length 2,  or classes
with a length but non-conforming `[` methods such that e.g.
x[length(x)]  would fail.

The idea of allowsInf() / allows.infinite() would be that you
typically would *NOT* define a method for your class usually,
and only define {if you want S4}

   setMethod("allowsInf", <myclass>, function(obj) TRUE)

for those cases where is.finite() and is.infinite() do work
sensibly for <myclass>, i.e., are vectorizing (and typically can
be both TRUE and FALSE)
*and* in case the default, i.e. allowsInf.default(),
is not already giving the correct result for <myclass> objects.

    [.......]

    > Put another way, and as pointed out by Bill above, the result of allowsInf
    > is really an attribute of a *class*, not of an object.

Well, yes, that's true, but that's also true e.g., for is.numeric()
.. one of the starting points of this RFC.

    > Its notable here that developers could also get around this by implementing
    > methods for the summary group generic that either implement the finite
    > argument or not as appropriate for their class, right? And that would be
    > true whether the default for, e.g., min and max were altered to have the
    > finite argument to match range, or not.

    > Best,
    > ~G

Sorry if I was confusing (much earlier):
I don't propose anymore --- at least not in this thread ---
that  min() and max() should  also get a 'finite = FALSE' optional argument.

This is about range(x, finite=TRUE)  to work (the "same" as the
default method), e.g. when x inherits from "Date" or "POSIXct"
*and* to do so in a somewhat smart way so that R developers of
other similar classes could also easily make range(*,
finite=TRUE)  "work"  for their class objects.

Martin


    > On Fri, May 19, 2023 at 8:30 AM Martin Maechler <maechler using stat.math.ethz.ch>
    > wrote:

    >> >>>>> Bill Dunlap
    >> >>>>>     on Thu, 11 May 2023 10:42:48 -0700 writes:
    >> 
    >> >> 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
    >> 
    >> yeah.. I agree that a general concept of such an interval class
    >> is even more flexible and generally useful.
    >> OTOH, people have already introduced such classes where they
    >> were really needed, and here it's really about
    >> *if*
    >> is.finite() and is.infinite() are also available and working
    >> but not always FALSE (which they are for logical, integer,
    >> character *and* raw, the latter really debatable - but *not* in this
    >> thread).
    >> 
    >> So, allows.infinite(x)  would *not* vectorize but return TRUE or
    >> FALSE (and typically not NA ..), in some sense being a property
    >> of class(x) only.
    >> 
    >> 
    >> > 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.
    >> >> >   }
    >> 
    >> it would have to include  is.complex() as well *and*
    >> in principle I'd want to *exclude* integers as they really
    >> cannot be +/- Inf
    >> ... but then you did say "not sure" ..
    >> 
    >> I'm still somewhat favoring this proposal,
    >> because it would be a bit more generally applicable
    >> but still very simple.
    >> 
    >> Personally, I'd go for the shorter allowsInf()  name,
    >> not adding another  <word1>.<word2>()  generic function,
    >> but that's less important and should not determine decisions I think.
    >> 
    >> Martin
    >> 
    >> >> >   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
    >> >> https://stat.ethz.ch/mailman/listinfo/r-devel
    >> >>
    >> 
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