[Rd] as.Date(Inf) displays as 'NA' but is actually 'Inf'

[Richard White]

Hi Gabriel,

The point is that it *visually* displays as NA, but is.na() still 
responds as FALSE.

When I (and I am sure many people) see an NA, we then use is.na(). If we 
see Inf displayed, we then use is.infinite(). With as.Date() this breaks 
down.

I'm not arguing that as.Date(Inf) should be coerced to NA. I'm arguing 
that as.Date(Inf) should be *visually* displayed as Inf (i.e. the 
truth!). I doubt this would break any existing code, because 
as.Date(Inf) acts as Inf in every way possible, except for when you 
visually look at the output printed on the screen.

William - For all the other Date bugs, they don't visually display false 
information about the variable's contents. They might give wrong output, 
but the output displayed is what exists inside the variable.

If we can't trust the R console to display the truth, then we are in a 
lot of trouble.

 > a <- as.Date(Inf, origin="2018-01-01")
 > a
[1] NA
 > is.na(a)
[1] FALSE

Richard

Gabriel Becker wrote on 06/03/2019 00:33:
> Richard,
>
> Well others may chime in here, but from a mathematical point of view, 
> the concept of "infinite days from right now" is well-defined, so it 
> maybe a "valid" date in that sense, but what day and month it will be 
> (year will be Inf) are indeterminate/not well defined. Those are 
> rightfully, NA, it seems?
>
> I mean you could disallow dates to take Inf at all, ever. I don't feel 
> strongly one way or the other about that, personally. That said, if 
> inf dates are allowed, its not clear to me that displaying the 
> "Formatted" date string as NA, even if the value isn't,  is wrong 
> given it can't be determined for that "date" is. It could be displayed 
> differently, I suppose, but all the ones I can think of off the top of 
> my head would be problematic and probably break lots of 
> formatted-dates parsing code out there in the wild (and in R, I would 
> guess). Things like displaying "Inf-NA-NA", or just "Inf". Neither of 
> those are going to handle a read-write round-trip well, I think.
>
> So my personal don't-really-have-a-hat-in-the-ring opinion would be to 
> either leave it as is, or force as.Date(Inf, bla) to actually be NA.
>
> Best,
> ~G
>
> On Tue, Mar 5, 2019 at 12:06 PM Richard White <w using rwhite.no 
> <mailto:w using rwhite.no>> wrote:
>
>     Hi,
>
>     I think I've discovered a bug in base R.
>
>     Basically, when using 'Inf' as as 'Date', is is visually displayed as
>     'NA', but R still treats it as 'Inf'. So it is very confusing to work
>     with, and can easily lead to errors:
>
>     # Visually displays as NA
>      > as.Date(Inf, origin="2018-01-01")
>     [1] NA
>
>     # Visually displays as NA
>      > str(as.Date(Inf, origin="2018-01-01"))
>     Date[1:1], format: NA
>
>     # Is NOT NA
>      > is.na <http://is.na>(as.Date(Inf, origin="2018-01-01"))
>     [1] FALSE
>
>     # Is still Inf
>      > is.infinite(as.Date(Inf, origin="2018-01-01"))
>     [1] TRUE
>
>     This gets really problematic when you are collapsing dates over
>     groups
>     and you want to find the first date of a group. Because min() returns
>     Inf if there is no data:
>
>     # Visually displays as NA
>      > as.Date(min(), origin="2018-01-01")
>     [1] NA
>     Warning message: In min() : no non-missing arguments to min;
>     returning Inf
>
>     # Visually displays as NA
>      > str(as.Date(min(), origin="2018-01-01"))
>     Date[1:1], format: NA
>     Warning message: In min() : no non-missing arguments to min;
>     returning Inf
>
>     # Is not NA
>      > is.na <http://is.na>(as.Date(min(), origin="2018-01-01"))
>     [1] FALSE
>     Warning message: In min() : no non-missing arguments to min;
>     returning Inf
>
>     # This is bad!
>      > as.Date(min(), origin="2018-01-01") > "2018-01-01"
>     [1] TRUE
>     Warning message: In min() : no non-missing arguments to min;
>     returning Inf
>
>     Here is my sessionInfo():
>
>      > sessionInfo()
>     R version 3.5.0 (2018-04-23)
>     Platform: x86_64-pc-linux-gnu (64-bit)
>     Running under: Debian GNU/Linux 9 (stretch)
>     Matrix products: default
>     BLAS: /usr/lib/openblas-base/libblas.so.3
>     LAPACK: /usr/lib/libopenblasp-r0.2.19.so
>     <http://libopenblasp-r0.2.19.so>
>
>     locale:
>     [1] LC_CTYPE=C.UTF-8 LC_NUMERIC=C LC_TIME=C.UTF-8 LC_COLLATE=C.UTF-8
>     LC_MONETARY=C.UTF-8
>     [6] LC_MESSAGES=C LC_PAPER=C.UTF-8 LC_NAME=C LC_ADDRESS=C
>     LC_TELEPHONE=C
>     [11] LC_MEASUREMENT=C.UTF-8 LC_IDENTIFICATION=C
>
>     attached base packages:
>     [1] stats graphics grDevices utils datasets methods base loaded via a
>     namespace (and not attached):
>     [1] compiler_3.5.0 tools_3.5.0 yaml_2.1.19
>
>      > Sys.getlocale()
>     [1]
>     "LC_CTYPE=C.UTF-8;LC_NUMERIC=C;LC_TIME=C.UTF-8;LC_COLLATE=C.UTF-8;LC_MONETARY=C.UTF-8;LC_MESSAGES=C;LC_PAPER=C.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=C.UTF-8;LC_IDENTIFICATION=C"
>
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