On 6/22/2011 1:23 PM, William Dunlap wrote:
The isdst value -1 doesn't seem right. Shouldn't it
be either 0 (not daylight savings time) or 1 (yes dst)?
I've only seen isdst==-1 when all the other entries
were NA (that happens when the string doesn't match
the format).
A isdst of -1 indicates that the dst status of that time is not known.
I've seen (and submitted patches to use) this when internally mucking
with the parts of a POSIXlt. Changing, say, the hour of a valid POSIXlt
value may result in a configuration which is not consistent (crossed a
DST boundary). This POSIXlt behaves fairly well, but when converted to
a POSIXct, gives NA. These conversions often happen behind the scenes.
In particular:
> is.na.POSIXlt
function (x)
is.na(as.POSIXct(x))
<environment: namespace:base>
It may be that as.POSIXct.POSIXlt can handle isdst==-1 when the DST
status is unambiguous, but maybe not when it is. I'm curious what the
specifics of the timezone Alexander is working in.
In the parts of the US where daylight savings time is
used the switchover took place near the beginning of
April in 1992, so you should have isdst=1 by May 3.
Perhaps you have an odd timezone file on your machine.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
-----Original Message-----
From: Alexander Shenkin [mailto:ashen...@ufl.edu]
Sent: Wednesday, June 22, 2011 1:07 PM
To: William Dunlap
Subject: Re: [R] strange date problem - May 3, 1992 is NA
Hi Bill,
Thanks for your reply. The results look almost identical to my eyes,
except for the mysterious "TRUE"...
methods("is.na")
[1] is.na.data.frame is.na.numeric_version is.na.POSIXlt
trace(methods("is.na"), quote(cat(" is.na: class(x)=",
class(x), "\n")))
Tracing function "is.na.data.frame" in package "base"
Tracing function "is.na.numeric_version" in package "base"
Tracing function "is.na.POSIXlt" in package "base"
[1] "is.na.data.frame" "is.na.numeric_version" "is.na.POSIXlt"
z<- strptime("5/3/1992", format="%m/%d/%Y")
is.na(z)
Tracing is.na.POSIXlt(z) on entry
is.na: class(x)= POSIXlt POSIXt
[1] TRUE
str(unclass(z))
List of 9
$ sec : num 0
$ min : int 0
$ hour : int 0
$ mday : int 3
$ mon : int 4
$ year : int 92
$ wday : int 0
$ yday : int 123
$ isdst: int -1
sessionInfo()
R version 2.12.1 (2010-12-16)
Platform: i386-pc-mingw32/i386 (32-bit)
locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] tools_2.12.1
thanks,
allie
On 6/22/2011 1:50 PM, William Dunlap wrote:
What do you get for the following commands, which
show which is.na method is getting called and
the internal structure of the dataset made
by strptime?
methods("is.na")
[1] is.na.data.frame is.na.numeric_version is.na.POSIXlt
trace(methods("is.na"), quote(cat(" is.na: class(x)=", class(x),
"\n")))
Tracing function "is.na.data.frame" in package "base"
Tracing function "is.na.numeric_version" in package "base"
Tracing function "is.na.POSIXlt" in package "base"
[1] "is.na.data.frame" "is.na.numeric_version" "is.na.POSIXlt"
z<- strptime("5/3/1992", format="%m/%d/%Y")
is.na(z)
Tracing is.na.POSIXlt(z) on entry
is.na: class(x)= POSIXlt POSIXt
[1] FALSE
str(unclass(z))
List of 9
$ sec : num 0
$ min : int 0
$ hour : int 0
$ mday : int 3
$ mon : int 4
$ year : int 92
$ wday : int 0
$ yday : int 123
$ isdst: int 1
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
-----Original Message-----
From: r-help-boun...@r-project.org
[mailto:r-help-boun...@r-project.org] On Behalf Of
Alexander Shenkin
Sent: Wednesday, June 22, 2011 11:41 AM
To: Sarah Goslee; r-help@r-project.org
Subject: Re: [R] strange date problem - May 3, 1992 is NA
On 6/22/2011 1:34 PM, Sarah Goslee wrote:
On Wed, Jun 22, 2011 at 2:28 PM, David Winsemius
<dwinsem...@comcast.net> wrote:
On Jun 22, 2011, at 2:03 PM, Sarah Goslee wrote:
Hi,
On Wed, Jun 22, 2011 at 11:40 AM, Alexander Shenkin
<ashen...@ufl.edu>
wrote:
is.na(strptime("5/2/1992", format="%m/%d/%Y"))
[1] FALSE
is.na(strptime("5/3/1992", format="%m/%d/%Y"))
[1] TRUE
I can't reproduce your problem on R 2.13.0 on linux:
I also cannot reproduce it on a Mac with 2.13.0 beta
Which strongly suggests that you should start by upgrading your R
installation if at all possible.
I'd also recommend trying it on a default R session, with no extra
packages loaded, and no items in your workspace. It's
possible that
something else is interfering.
On linux, that's achieved by typing R --vanilla at the
command line.
I'm afraid I don't know how to do it for Windows, but should be
similarly straightforward.
Thanks Sarah. Still getting the problem. I should surely
upgrade, but
still, not a bad idea to get to the bottom of this, or at
least have it
documented as a known issue. BTW, I'm on Windows 7 Pro x64.
(running Rgui.exe --vanilla):
is.na(strptime("5/3/1992", format="%m/%d/%Y"))
[1] TRUE
is.na(strptime("5/2/1992", format="%m/%d/%Y"))
[1] FALSE
sessionInfo()
R version 2.12.1 (2010-12-16)
Platform: i386-pc-mingw32/i386 (32-bit)
locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252
attached base packages:
[1] stats graphics grDevices utils datasets
methods base
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