as.character.POSIXt in R devel

Thu, Oct 6, 2022 3:20 AM

In?'as.character.POSIXt'?in?R?devel?after?r83010:
????????????if(getOption("OutDec")?!=?OutDec)?{?op?<-?options(OutDec?=?OutDec);?on.exit(op)?}

on.exit(op)
does?nothing.?It?should?be
on.exit(options(op))


Is?it?OK?to?output?the?seconds?using?scientific?notation?
Example?(modified?from?https://bugs.r-project.org/show_bug.cgi?id=9819):
op?<-?options(scipen?=?0)?#?(default?setting)
as.character(as.POSIXlt("2007-07-27?16:11:00.000002"))
#?"2007-07-27?16:11:02e-06"
options(op)


Example (modified from https://bugs.r-project.org/show_bug.cgi?id=14579):
op?<-?options(scipen?=?0)?#?(default?setting)
ct <- as.POSIXct(1302811200 - 2e-07,
origin = as.POSIXct("1970-01-01 00:00:00", tz="UTC"), tz = "UTC")
as.character(ct) # outputs "60" for seconds
# "2011-04-14 19:59:60"
options(op)


(CharleMagne.crowned?<-?as.POSIXlt(ISOdate(774,7,10)))
as.character(CharleMagne.crowned)

As?I?mentioned,?they?are?different?on?OSes?_other?than_?Linux.

In?R?on?Windows:

[1]?"0774-07-10?12:00:00?GMT"


-----------------------

On?Monday,?3?October?2022,?11:58:53?pm?GMT+7,?Martin?Maechler?<maechler at stat.math.ethz.ch>?wrote:

????>>?With?r82904,?'as.character.POSIXt'?in?R?devel?is?changed.?The?NEWS?item:

????>>?as.character(<POSIXt>)?now?behaves?more?in?line?with?the
????>>?methods?for?atomic?vectors?such?as?numbers,?and?is?no?longer
????>>?influenced?by?options().

[..............]

????>>?*?Wrong:

????>>?The?result?is?wrong?when?as.character(fs[n0])?has?scientific?notation.

????>?yes,?you?are?right.??This?is?a?lapsus?I?will?fix.

????>>?Example?(modified?from?https://bugs.r-project.org/show_bug.cgi?id=9819):
????>>?op?<-?options(scipen?=?0,?OutDec?=?".")?#?(default?setting)
????>>?x?<-?as.POSIXlt("2007-07-27?16:11:03.000002")
????>>?as.character(x)
????>>?#?"2007-07-27?16:11:03.99999999983547e-06"
????>>?as.character(x$sec?-?trunc(x$sec))
????>>?#?"1.99999999983547e-06"
????>>?options(op)

????>>?'as.character.POSIXt'?could?temporarily?set?option?'scipen'?large?enough?to?prevent?scientific?notation?in?as.character(fs[n0])?.

????>?Yes,?something?like?that.

I?have?committed?a?version?now?of?datetime.R,??svn?rev?83010?,
which?does?no?longer?depend?on??'OutDec'?(but?gets?such?argument)
and?which?has?a?new?'digits'?argument?which?defaults
to?14?for?POSIXlt?and
to??6?for?POSIXct??..?but?the?user?can?choose?a?different?value.

Also,?it?now?uses?the?equivalent?of??as.character(round(x$sec,?digits))
(in?case?the?seconds?need?to?be?shown)??which?also?solves?the
following??"too?much?precision"??problem.

????>>?*?Too?much?precision:

????>>?In?some?cases?with?fractional?seconds?with?seconds?close?to?60,?the?result?has?many?decimal?places?while?there?is?an?accurate?representation?with?less?decimal?places.?It?is?actually?OK,?just?unpleasant.

????>?I?agree?that?is?unpleasant.
????>?To?someone?else?I?had?written?that?we?also?may?need?to?improve
????>?the?number?of?decimals?shown?here.
????>?The?design?has?been?that?it?should?be?"full?precision"
????>?as?it?is?for??as.character(<numbers>)

????>?Now,?we?know?that?POSIXct?cannot?be?very?precise?(in?its
????>?fractional?seconds)?but?that?is?very?different?for?POSIXlt?where
????>?fractional?seconds?may?have?14?digits?after?the?decimal?point.

????>?Ideally?we?could?*store*?with?the?POSIXlt?object?if?it?was
????>?produced?from?a?POSIXct?one,?and?hence?have?only?around?6?valid?digits
????>?(after?the?dec.)?or?not.??As?we?cannot?currently?store/save?that
????>?info,?we?kept?using?"full"?precision?which?may?be?much?more?than
????>?is?sensible.

????>>?Example?(modified?from?https://bugs.r-project.org/show_bug.cgi?id=14693):
????>>?op?<-?options(scipen?=?0,?OutDec?=?".")?#?(default?setting)
????>>?x?<-?as.POSIXlt("2011-10-01?12:34:56.3")
????>>?x$sec?==?56.3?#?TRUE

????>?[which?may?be?typical,?but?may?also?be?platform?dependent]

????>>?print(x$sec,?17)
????>>?#?[1]?56.299999999999997
????>>?as.character(x)
????>>?#?"2011-10-01?12:34:56.299999999999997"
????>>?format(x,?"%Y-%m-%d?%H:%M:%OS1")?#?short?and?accurate
????>>?#?"2011-10-01?12:34:56.3"
????>>?ct?<-?as.POSIXct(x,?tz?=?"UTC")
????>>?identical(ct,
????>>?as.POSIXct("2011-10-01?12:34:56.3",?tz?=?"UTC"))
????>>?#?TRUE
????>>?print(as.numeric(ct),?17)
????>>?#?[1]?1317472496.3
????>>?lct?<-?as.POSIXlt(ct)
????>>?lct$sec?==?56.3?#?FALSE
????>>?print(lct$sec,?17)
????>>?#?[1]?56.299999952316284
????>>?as.character(ct)
????>>?#?"2011-10-01?12:34:56.299999952316284"
????>>?options(op)

????>>?The?"POSIXct"?case?is?a?little?different?because?some?precision?is?already?lost?after?converted?to?"POSIXct".

????>?yes,?indeed.

????>>?In?'as.character.POSIXt',?using?'as.character'?on?the?seconds?(not?separating?the?fractional?part)?might?be?good?enough,?but?a?leading?zero?must?be?added?as?necessary.

????>?I?think?you?are?right:?that?may?definitely?better...

indeed;?part?of?my?commit.

????>>?*?Different?from?'format':

????>>?-?With?fractional?seconds,?the?result?is?influenced?by?option?'OutDec'.

this?has?been?solved,?too.
For?the?"freaks"?allowing?an?explicit??'OutDec?=?*'?argument
but?*not*?with?default?depending?on?options()!


????>?Thank?you.??I?was?not?aware?of?that.
????>?The?reason?"of?course"?being?that??as.character(<numeric>)??is
????>?*also*?depending?on?option??OutDec.

????>?I?would?say?that?is?clearly?wrong...??and?I?think?we?should
????>?strongl?consider?to?change?that:

????>?'OutDec'?should?influence?print()ing?and?format()ing??but?should
????>?*not*?influence??as.character()??at?least?not?for?basic?R?types/objects.


????>>?-?From?"Printing?years"?in??strptime:?"For?years?0?to?999?most?OSes?pad?with?zeros?or?spaces?to?4?characters,?and?Linux?outputs?just?the?number."
????>>?Because?(1900?+?x$year)?is?formatted?with?%d?in?'as.character.POSIXt',?years?0?to?999?is?output?without?padding.?It?is?different?from?'format'?in?OSes?other?than?Linux.

????>?Good?point.??This?should?be??amended.

Not?yet.??Actually,?I'm?no?longer?sure?this?needs?any?action.
I?find?it?somewhat?natural?that

[1]?"774-07-10?12:00:00?GMT"

[1]?"774-07-10?12:00:00"


[snip]

as.character.POSIXt in R devel

Thread (5 messages)