[R] POSIXct bug for conversion of specific combinations of date and time

[Jeff Newmiller]

There have been a couple of threads recently on proper usage of POSIXct. I suggest you read the archives.

After you read the archives: In your case, you don't seem to have zone offset data in your time info, so you probably need to use Sys.setenv to set an appropriate default time zone. The NA values are likely due to your current (unspecified) computer time zone. If you want to follow up, we are probably going to need you to indicate what Sys.getenv("TZ") and sessionInfo() report (per the Posting Guide mentioned at the bottom of this email).
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Sent from my phone. Please excuse my brevity.

"Carlos André Zucco" <cazucco14 at gmail.com> wrote:
>Hello everyone,
>
>I'm having a big trouble with which seems to be a bug in as.POSIXct()
>date-time conversion. I have massive GPS datasets in which each
>location
>has it's own date and time attribute. As I convert them to POSIXct
>format,
>1300 cases (of about half a million locations) simply return NA values.
>
>I picked up a small sample of failed cases and normal cases to
>demonstrate
>the problem (see below). Can anyone understand what's happening
>Thanks
>
>## Data input
>>date<-rep("2012/10/21", 14)
>>hour<-
>c("00:02:38","00:11:05","00:19:33","00:28:00","00:36:27","00:44:57",
>+"00:53:27","01:03:28","01:10:15","01:16:34","01:24:00","01:30:13","01:47:58",
>+"01:52:43")
>>time<-as.data.frame(cbind(date,hour))
># as.POSIXct formating
>time$convert<-as.POSIXct(paste(time[,1],time[,2]),format="%Y/%m/%d
>%H:%M:%S")
>         date     hour             convert
>1  2012/10/21 00:02:38                <NA>
>2  2012/10/21 00:11:05                <NA>
>3  2012/10/21 00:19:33                <NA>
>4  2012/10/21 00:28:00                <NA>
>5  2012/10/21 00:36:27                <NA>
>6  2012/10/21 00:44:57                <NA>
>7  2012/10/21 00:53:27                <NA>
>8  2012/10/21 01:03:28 2012-10-21 01:03:28
>9  2012/10/21 01:10:15 2012-10-21 01:10:15
>10 2012/10/21 01:16:34 2012-10-21 01:16:34
>11 2012/10/21 01:24:00 2012-10-21 01:24:00
>12 2012/10/21 01:30:13 2012-10-21 01:30:13
>13 2012/10/21 01:47:58 2012-10-21 01:47:58
>14 2012/10/21 01:52:43 2012-10-21 01:52:43
>## Se that the problem occur specifically with information concerning
>21/oct/2012 between midnight and 1am
>
># alternatively strptime converting
>>time$convert<-strptime(paste(time[,1],time[,2]),format="%Y/%m/%d
>%H:%M:%S")
>>time$convert
>         date     hour             convert
>1  2012/10/21 00:02:38 2012-10-21 00:02:38
>2  2012/10/21 00:11:05 2012-10-21 00:11:05
>3  2012/10/21 00:19:33 2012-10-21 00:19:33
>4  2012/10/21 00:28:00 2012-10-21 00:28:00
>5  2012/10/21 00:36:27 2012-10-21 00:36:27
>6  2012/10/21 00:44:57 2012-10-21 00:44:57
>7  2012/10/21 00:53:27 2012-10-21 00:53:27
>8  2012/10/21 01:03:28 2012-10-21 01:03:28
>9  2012/10/21 01:10:15 2012-10-21 01:10:15
>10 2012/10/21 01:16:34 2012-10-21 01:16:34
>11 2012/10/21 01:24:00 2012-10-21 01:24:00
>12 2012/10/21 01:30:13 2012-10-21 01:30:13
>13 2012/10/21 01:47:58 2012-10-21 01:47:58
>14 2012/10/21 01:52:43 2012-10-21 01:52:43
># seems ok, however try any further commands:
>>range(time$convert)
>[1] NA NA
>>min(time$convert)
>[1] NA
>>time$convert[1] - time$convert[2]
>Time difference of NA secs
>
> Just in case it helps my session information area
>> sessionInfo()
>R version 2.15.1 (2012-06-22)
>Platform: i386-pc-mingw32/i386 (32-bit)
>
>locale:
>[1] LC_COLLATE=Portuguese_Brazil.1252  LC_CTYPE=Portuguese_Brazil.1252
>[3] LC_MONETARY=Portuguese_Brazil.1252 LC_NUMERIC=C
>[5] LC_TIME=Portuguese_Brazil.1252
>
>attached base packages:
>[1] stats     graphics  grDevices utils     datasets  methods   base
>
>loaded via a namespace (and not attached):
>[1] grid_2.15.1    lattice_0.20-6 nlme_3.1-104
>
>
>
>*Carlos Andr� Zucco*
>---------------------------------------------------------------------------------
>Bi�logo, Mestre em Ecologia
>Laborat�rio de Ecologia e Conserva��o de Popula��es (LECP/IB/UFRJ)
>Doutorando do Programa de P�s-gradua��o em Ecologia da UFRJ
>---------------------------------------------------------------------------------
>
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>
>
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