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" <cazucc...@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
>---------------------------------------------------------------------------------
>
> [[alternative HTML version deleted]]
>
>
>
>------------------------------------------------------------------------
>
>______________________________________________
>R-help@r-project.org mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.
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