Technically, there is a round() for 'Date' objects, but it doesn't
seem very useful, because it basically just fall back to the default
round() method, which only takes the 'digits' argument.
Here's an example:
date <- Sys.Date()
class(date)
[1] "Date"
We see that there are only two round() methods in addition to the
implicit built-in one;
methods("round")
[1] round.Date round.POSIXt
see '?methods' for accessing help and source code
Looking at round() for 'Date';
round.Date
function (x, ...)
{
.Date(NextMethod(), oldClass(x))
}
<environment: namespace:base>
we see that it defers to the next method here, which is the built-in
one. The built-in one, only accepts 'digits', which does nothing for
digits >= 0. For digits < 0, it rounds to power of ten, e.g.
date
[1] "2024-02-08"
round(date, digits = 0)
[1] "2024-02-08"
round(date, digits = 1)
[1] "2024-02-08"
round(date, digits = 2)
[1] "2024-02-08"
round(date, digits = -1)
[1] "2024-02-07"
round(date, digits = -2)
[1] "2024-03-18"
round(date, digits = -3)
[1] "2024-10-04"
round(date, digits = -4)
[1] "2024-10-04"
round(date, digits = -5)
[1] "1970-01-01"
So, although technically invalid, OPs remark is a valid one. I'd also
expect `round()` for Date to support 'units' similar to timestamps,
e.g.
time <- Sys.time()
class(time)
[1] "POSIXct" "POSIXt"
time
[1] "2024-02-08 09:17:02 PST"
round(time, units = "days")
[1] "2024-02-08 PST"
round(time, units = "months")
[1] "2024-02-01 PST"
round(time, units = "years")
[1] "2024-01-01 PST"
So, I agree with OP that one would expect:
round(date, units = "days")
[1] "2024-02-08"
round(date, units = "months")
[1] "2024-02-01"
round(date, units = "years")
[1] "2024-01-01"
to also work here.
FWIW, I don't think we want to encourage circumventing the S3 generic
and calling S3 methods directly, i.e. I don't recommend doing things
like round.POSIXt(...). Ideally, all S3 methods in R would be
non-exported, but some remain exported for legacy reason. But, I think
we should treat them as if they in the future will become
non-exported.
/Henrik
On Thu, Feb 8, 2024 at 8:18 AM Olivier Benz via R-devel
<r-devel@r-project.org> wrote:
On 8 Feb 2024, at 15:15, Martin Maechler <maech...@stat.math.ethz.ch> wrote:
Jiří Moravec
on Wed, 7 Feb 2024 10:23:15 +1300 writes:
This is my first time working with dates, so if the answer is "Duh, work
with POSIXt", please ignore it.
Why is not `round.Date` and `trunc.Date` "implemented" for `Date`?
Is this because `Date` is (mostly) a virtual class setup for a better
inheritance or is that something that is just missing? (like
`sort.data.frame`). Would R core welcome a patch?
I decided to convert some dates to date using `as.Date` function, which
converts to a plain `Date` class, because that felt natural.
But then when trying to round to closest year, I have realized that the
`round` and `trunc` for `Date` do not behave as for `POSIXt`.
I would assume that these will have equivalent output:
Sys.time() |> round("years") # 2024-01-01 NZDT
Sys.Date() |> round("years") # Error in round.default(...): non-numeric
argument to mathematical function
Looking at the code (and reading the documentation more carefully) shows
the issue, but this looks like an omission that should be patched.
-- Jirka
You are wrong: They *are* implemented,
both even visible since they are in the 'base' package!
==> they have help pages you can read ....
Here are examples:
trunc(Sys.Date())
[1] "2024-02-08"
trunc(Sys.Date(), "month")
[1] "2024-02-01"
trunc(Sys.Date(), "year")
[1] "2024-01-01"
Maybe he meant
r$> Sys.time() |> round.POSIXt("years")
[1] "2024-01-01 CET"
r$> Sys.Date() |> round.POSIXt("years")
[1] "2024-01-01 UTC"
The only difference is the timezone
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On Thu, Feb 8, 2024 at 9:06 AM Rui Barradas <ruipbarra...@sapo.pt> wrote:
Às 14:36 de 08/02/2024, Olivier Benz via R-devel escreveu:
On 8 Feb 2024, at 15:15, Martin Maechler <maech...@stat.math.ethz.ch> wrote:
Jiří Moravec
on Wed, 7 Feb 2024 10:23:15 +1300 writes:
This is my first time working with dates, so if the answer is "Duh, work
with POSIXt", please ignore it.
Why is not `round.Date` and `trunc.Date` "implemented" for `Date`?
Is this because `Date` is (mostly) a virtual class setup for a better
inheritance or is that something that is just missing? (like
`sort.data.frame`). Would R core welcome a patch?
I decided to convert some dates to date using `as.Date` function, which
converts to a plain `Date` class, because that felt natural.
But then when trying to round to closest year, I have realized that the
`round` and `trunc` for `Date` do not behave as for `POSIXt`.
I would assume that these will have equivalent output:
Sys.time() |> round("years") # 2024-01-01 NZDT
Sys.Date() |> round("years") # Error in round.default(...): non-numeric
argument to mathematical function
Looking at the code (and reading the documentation more carefully) shows
the issue, but this looks like an omission that should be patched.
-- Jirka
You are wrong: They *are* implemented,
both even visible since they are in the 'base' package!
==> they have help pages you can read ....
Here are examples:
trunc(Sys.Date())
[1] "2024-02-08"
trunc(Sys.Date(), "month")
[1] "2024-02-01"
trunc(Sys.Date(), "year")
[1] "2024-01-01"
Maybe he meant
r$> Sys.time() |> round.POSIXt("years")
[1] "2024-01-01 CET"
r$> Sys.Date() |> round.POSIXt("years")
[1] "2024-01-01 UTC"
The only difference is the timezone
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Hello,
You are right that the timezones are different but Sys.date() returns an
object of class "Date" so the method called is not that one.
Here an example with trunc.
Sys.Date() |> class()
Sys.Date() |> trunc("years")
Sys.Date() |> trunc.Date("years")
Sys.Date() |> trunc.POSIXt("years")
As for the OP, the problem is thhat the generic roun())) doesn't have
unit argument. So I am nnnot understanding why round.POSIXt works.
Sys.Date() |> round("years")
#> Error in round.default(structure(19761, class = "Date"), "years"):
non-numeric argument to mathematical function
Sys.Date() |> round.Date("years")
#> Error in NextMethod(): generic function not specified
Sys.Date() |> round.POSIXt("years")
#> [1] "2024-01-01 UTC"
Sys.Date() |> round.POSIXt("months")
#> [1] "2024-02-01 UTC"
Sys.Date() |> round.POSIXt("days")
#> [1] "2024-02-08 UTC"
Hope this helps,
Rui Barradas
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