[Rd] [R] R-3.4.0 fails test

Joris Meys jorismeys at gmail.com
Thu May 18 13:47:28 CEST 2017


Correction: Also dlt uses the default timezone, but POSIXlt is not
recalculated whereas POSIXct is. Reason for that is the different way
values are stored (hours, minutes, seconds as opposed to minutes from
origin, as explained in my previous mail)

CHeers
Joris

On Thu, May 18, 2017 at 1:45 PM, Joris Meys <jorismeys at gmail.com> wrote:

> This has to do with your own timezone. If I run that code on my computer,
> both formats are correct. If I do this after
>
> Sys.setenv(TZ = "UTC")
>
> Then:
>
> > cbind(format(dlt), format(dct))
>       [,1]                  [,2]
>  [1,] "2016-12-06 21:45:41" "2016-12-06 20:45:41"
>  [2,] "2016-12-06 21:45:42" "2016-12-06 20:45:42"
>
> The reason for that, is that dlt has a timezone set, but dct doesn't. To
> be correct, it only takes the first value "", which indicates "Use the
> default timezone of the locale".
>
> > attr(dlt, "tzone")
> [1] ""     "CET"  "CEST"
> > attr(dct, "tzone")
> [1] ""
>
> The thing is, in POSIXlt the timezone attribute is stored together with
> the actual values for hour, minute etc. in list format. Changing the
> timezone doesn't change those values, but it will change the time itself:
>
> > Sys.unsetenv("TZ")
> > dlt2 <- dlt
> > attr(dlt2,"tzone") <- "UTC"
> > dlt2
>  [1] "2016-12-06 21:45:41 UTC" "2016-12-06 21:45:42 UTC"
>  [3] "2016-12-06 21:45:43 UTC" "2016-12-06 21:45:44 UTC"
>
> in POSIXct the value doesn't change either, just the attribute. But this
> value is the number of seconds since the origin. So the time itself doesn't
> change, but you'll see a different hour.
>
> > dct
>  [1] "2016-12-06 21:45:41 CET" "2016-12-06 21:45:42 CET"
> ...
> > attr(dct,"tzone") <- "UTC"
> > dct
>  [1] "2016-12-06 20:45:41 UTC" "2016-12-06 20:45:42 UTC"
>  [3] "2016-12-06 20:45:43 UTC" "2016-12-06 20:45:44 UTC"
>
> So what you see, is simply the result of your timezone settings on your
> computer.
>
> Cheers
> Joris
>
> On Thu, May 18, 2017 at 1:19 PM, peter dalgaard <pdalgd at gmail.com> wrote:
>
>>
>> > On 18 May 2017, at 11:00 , Patrick Connolly <p_connolly at slingshot.co.nz>
>> wrote:
>> >
>> > On Wed, 17-May-2017 at 01:21PM +0200, Peter Dalgaard wrote:
>> >
>> > |>
>> > |> Anyways, you might want to
>> > |>
>> > |> a) move the discussion to R-devel
>> > |> b) include your platform (hardware, OS) and time zone info
>> >
>> > System:    Host: MTA-V1-427894 Kernel: 3.19.0-32-generic x86_64 (64 bit
>> gcc: 4.8.2)
>> >           Desktop: KDE Plasma 4.14.2 (Qt 4.8.6) Distro: Linux Mint 17.3
>> Rosa
>>
>> I suppose that'll do...
>>
>>
>> > Time zone: NZST
>>
>>
>>
>> >
>> > |> c) run the offending code lines "by hand" and show us the values of
>> format(dlt) and format(dct) so we can see what the problem is, something
>> like
>> > |>
>> > |> dlt <- structure(
>> > |>     list(sec = 52, min = 59L, hour = 18L, mday = 6L, mon = 11L, year
>> = 116L,
>> > |>        wday = 2L, yday = 340L, isdst = 0L, zone = "CET", gmtoff =
>> 3600L),
>> > |>        class = c("POSIXlt", "POSIXt"), tzone = c("", "CET", "CEST"))
>> > |> dlt$sec <- 10000 + 1:10
>> > |> dct <- as.POSIXct(dlt)
>> > |> cbind(format(dlt), format(dct))
>> >
>> >> cbind(format(dlt), format(dct))
>> >      [,1]                  [,2]
>> > [1,] "2016-12-06 21:45:41" "2016-12-06 22:45:41"
>> > [2,] "2016-12-06 21:45:42" "2016-12-06 22:45:42"
>> > [3,] "2016-12-06 21:45:43" "2016-12-06 22:45:43"
>> > [4,] "2016-12-06 21:45:44" "2016-12-06 22:45:44"
>> > [5,] "2016-12-06 21:45:45" "2016-12-06 22:45:45"
>> > [6,] "2016-12-06 21:45:46" "2016-12-06 22:45:46"
>> > [7,] "2016-12-06 21:45:47" "2016-12-06 22:45:47"
>> > [8,] "2016-12-06 21:45:48" "2016-12-06 22:45:48"
>> > [9,] "2016-12-06 21:45:49" "2016-12-06 22:45:49"
>> > [10,] "2016-12-06 21:45:50" "2016-12-06 22:45:50"
>> >>
>> >
>>
>>
>> So exactly 1 hour out of whack. Is there a Daylight Saving Times issue,
>> perchance?
>>
>> -pd
>>
>>
>> >
>> > --
>> > ~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.
>> ~.~.~.~.~.~.
>> >   ___    Patrick Connolly
>> > {~._.~}                   Great minds discuss ideas
>> > _( Y )_                Average minds discuss events
>> > (:_~*~_:)                  Small minds discuss people
>> > (_)-(_)                             ..... Eleanor Roosevelt
>> >
>> > ~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.
>> ~.~.~.~.~.~.
>>
>> --
>> Peter Dalgaard, Professor,
>> Center for Statistics, Copenhagen Business School
>> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
>> Phone: (+45)38153501
>> Office: A 4.23
>> Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com
>>
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>
>
>
>
> --
> Joris Meys
> Statistical consultant
>
> Ghent University
> Faculty of Bioscience Engineering
> Department of Mathematical Modelling, Statistics and Bio-Informatics
>
> tel :  +32 (0)9 264 61 79 <+32%209%20264%2061%2079>
> Joris.Meys at Ugent.be
> -------------------------------
> Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php
>



-- 
Joris Meys
Statistical consultant

Ghent University
Faculty of Bioscience Engineering
Department of Mathematical Modelling, Statistics and Bio-Informatics

tel :  +32 (0)9 264 61 79
Joris.Meys at Ugent.be
-------------------------------
Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php

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