R devel - May 2017 - [R] R-3.4.0 fails test

> On 18 May 2017, at 14:58 , Martyn Plummer <plummerM at iarc.fr>
wrote:
> 
> 
> 
>> On 18 May 2017, at 14:51, peter dalgaard <pdalgd at gmail.com>
wrote:
>> 
>> 
>>> On 18 May 2017, at 13:47 , Joris Meys <jorismeys at
gmail.com> wrote:
>>> 
>>> 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)
>>> 
>> 
>> I would suspect that there is something more subtle going on, New
Zealand time is 10, 11, or 12 hours from Central European, depending on time of
year (10 in our Summer, 12 in theirs and 11 during the overlap at both ends, if
you must know), and we are talking a 1 hour difference.
>> 
>> However DST transitions were both in March/April, so that's not it.
Maybe a POSIX[lc]t expert can comment?
> 
> If I change the month from December to June then I see the same phenomenon
in my Europe/Paris time zone. The issue seems to be that, for the date chosen
for the test, Summer/daylight savings time is in force in NZ and some other
parts of the southern hemisphere , but not in the northern hemisphere.
> 
Of course! I overlooked that the date in the test is the issue, not the current
date. (Let's blame that on the fact that Summer seems to have finally
arrived in Copenhagen...)

"svn praise" claims this test is due to Martin Maechler in r71742, so
maybe he knows how to fix it. (I wonder if he just used the current date at the
time, or actually thought that there would be no DST issues in December ;-) )

-pd

> Martyn
> 
>> -pd
>> 
>>> 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
>>> 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
>> 
>> -- 
>> 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
> -----------------------------------------------------------------------
> This message and its attachments are strictly confiden...{{dropped:25}}

> > On 18 May 2017, at 14:58 , Martyn Plummer <plummerM at iarc.fr>
wrote:
> > 
> >> On 18 May 2017, at 14:51, peter dalgaard <pdalgd at
gmail.com> wrote:
> >>> On 18 May 2017, at 13:47 , Joris Meys <jorismeys at
gmail.com> wrote:
> >>> 
> >>> 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)
> >>> 
> >> 
> >> I would suspect that there is something more subtle going on, New
Zealand time is 10, 11, or 12 hours from Central European, depending on time of
year (10 in our Summer, 12 in theirs and 11 during the overlap at both ends, if
you must know), and we are talking a 1 hour difference.
> >> 
> >> However DST transitions were both in March/April, so that's
not it. Maybe a POSIX[lc]t expert can comment?
> > 
> > If I change the month from December to June then I see the same
phenomenon in my Europe/Paris time zone. The issue seems to be that, for the
date chosen for the test, Summer/daylight savings time is in force in NZ and
some other parts of the southern hemisphere , but not in the northern
hemisphere.
> > 
> Of course! I overlooked that the date in the test is the issue, not the
current date. (Let's blame that on the fact that Summer seems to have
finally arrived in Copenhagen...)
> "svn praise" claims this test is due to Martin Maechler in
r71742, so maybe he knows how to fix it. (I wonder if he just used the current
date at the time, or actually thought that there would be no DST issues in
December ;-) )
> -pd
I think the former.  This was about fixing a segmentation fault problem
 (thread from Dec 6, 2016, on the R-devel mailing list, starting
  here: https://stat.ethz.ch/pipermail/r-devel/2016-December/073448.html )
mostly,  but the 2nd part of the regression test evidently needs
more thought than I had put there.

Being pretty "stretched" time wise currently, I'm happy for
timezone-portable propositions to change the test.

Martin

On Thu, 18-May-2017 at 05:46PM +0200, Martin Maechler wrote:

|> 
.....

|> 
|> Being pretty "stretched" time wise currently, I'm happy for
|> timezone-portable propositions to change the test.

Meantime, anyone who lives where DST happpens in December who wants to
get through the remaining tests can avoid this one by changing the line
> stopifnot(length(fd) == 10, identical(fd, format(dct <-
as.POSIXct(dlt))))
to
> stopifnot(length(fd) == 10, identical(fd, format(dct <-
as.POSIXlt(dlt))))
                                                                ^^^^
(which effectively isn't testing anything much)

A less lazy way would be to comment out the relevant lines.


|> 
|> Martin

-- 
~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.   
   ___    Patrick Connolly   
 {~._.~}                   Great minds discuss ideas    
 _( Y )_  	         Average minds discuss events 
(:_~*~_:)                  Small minds discuss people  
 (_)-(_)  	                      ..... Eleanor Roosevelt
	  
~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.