RE: [R] POSIX problem

From: Mulholland, Tom <Tom.Mulholland_at_dpi.wa.gov.au>
Date: Wed 01 Jun 2005 - 10:42:22 EST


Well I skipped to the end so pardon me if I've missed something. My first reaction was to go and look at the excellent article by Gabor in RNews 2004-1 on dates (p.32 in particular)

> as.POSIXct(strptime("7/12/2001 10:32",format = "%d/%m/%Y %H:%M"))
[1] "2001-12-07 10:32:00 W. Australia Standard Time"

as.POSIXct handles a limited number of formats and does not have a "format" parameter.

> args(as.POSIXct)

function (x, tz = "")

So you need to use strptime.

Tom

> -----Original Message-----
> From: r-help-bounces@stat.math.ethz.ch
> [mailto:r-help-bounces@stat.math.ethz.ch]On Behalf Of David Scott
> Sent: Tuesday, 31 May 2005 8:27 PM
> To: r-help@stat.math.ethz.ch
> Subject: [R] POSIX problem
>
>
>
> I am having trouble with creating a POSIXct object. If I
> create a variable
> of class Date first out of the date part of my data, I am ok,
> but if I
> just paste the date and time parts together and try and
> create the POSIXct
> object, I have problems.
>
> Here is a toy example created from the actual data which caused the
> problem. I am using R 2.0.1 on Windows XP.
>
> > # Data frame with dates and times, as character
> > PeopleData.df
> StartDate StartTime
> 1 29/10/2001 15:26
> 2 7/12/2001 10:32
> 3 16/11/2001 13:58
> 4 28/11/2001 14:00
> 5 2/11/2001 15:22
> 6 26/11/2001 11:15
> > str(PeopleData.df)
> `data.frame': 6 obs. of 2 variables:
> $ StartDate: chr "29/10/2001" "7/12/2001" "16/11/2001"
> "28/11/2001" ...
> $ StartTime: chr "15:26" "10:32" "13:58" "14:00" ...
> > dput(PeopleData.df)
> structure(list(StartDate = c("29/10/2001", "7/12/2001", "16/11/2001",
> "28/11/2001", "2/11/2001", "26/11/2001"), StartTime = c("15:26",
> "10:32", "13:58", "14:00", "15:22", "11:15")), .Names = c("StartDate",
> "StartTime"), row.names = c("1", "2", "3", "4", "5", "6"), class =
> "data.frame")
> > BeginDate <- as.Date(PeopleData.df$StartDate,format="%d/%m/%Y")
> > BeginDate
> [1] "2001-10-29" "2001-12-07" "2001-11-16" "2001-11-28" "2001-11-02"
> [6] "2001-11-26"
> > # Create POSIXct date-time object without difficulty
> > BeginTime <-
> as.POSIXct(format(paste(BeginDate,PeopleData.df$StartTime),
> + format="%Y/%m/%d %H:%M"))
> > BeginTime
> [1] "2001-10-29 15:26:00 New Zealand Standard Time"
> [2] "2001-12-07 10:32:00 New Zealand Standard Time"
> [3] "2001-11-16 13:58:00 New Zealand Standard Time"
> [4] "2001-11-28 14:00:00 New Zealand Standard Time"
> [5] "2001-11-02 15:22:00 New Zealand Standard Time"
> [6] "2001-11-26 11:15:00 New Zealand Standard Time"
> > # But not directly from the dates and times
> > BeginTime <-
> as.POSIXct(format(paste(PeopleData.df$StartDate,PeopleData.df$
> StartTime),
> + format="%d/%m/%Y %H:%M"))
> > BeginTime
> [1] "0029-10-20 New Zealand Standard Time"
> [2] "0007-12-20 New Zealand Standard Time"
> [3] "0016-11-20 New Zealand Standard Time"
> [4] "0028-11-20 New Zealand Standard Time"
> [5] "0002-11-20 New Zealand Standard Time"
> [6] "0026-11-20 New Zealand Standard Time"
> > # Format looks correct to me
> > paste(PeopleData.df$StartDate,PeopleData.df$StartTime)
> [1] "29/10/2001 15:26" "7/12/2001 10:32" "16/11/2001 13:58"
> "28/11/2001
> 14:00"
> [5] "2/11/2001 15:22" "26/11/2001 11:15"
>
> What I think might be causing the problem is the lack of a
> leading zero
> for some of the days (as in 7/12/2001). This doesn't phase
> as.Date though.
>
> David Scott
>
>
>
> _________________________________________________________________
> David Scott Department of Statistics, Tamaki Campus
> The University of Auckland, PB 92019
> Auckland NEW ZEALAND
> Phone: +64 9 373 7599 ext 86830 Fax: +64 9 373 7000
> Email: d.scott@auckland.ac.nz
>
>
> Graduate Officer, Department of Statistics
>
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R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Jun 01 10:47:38 2005

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