[R] about data format in R

[lily li]

Thanks. It seems that substrings only subset the data, not convert the
format. For example, I use the code below:
DF$time = substring(DF$time, '%Y-%m-%d')

where DF$time has the structure:
'2002-01-01 00:00:00', '2002-01-01 12:00:00', '2003-01-01 00:00:00',
'2003-01-01 12:00:00', etc.
I wanted to convert the 'time' column to '2002-01-01', '2002-01-01',
'2003-01-01', '2003-01-01', etc.

Using the code above, it gives the error message:
Error in as.POSIXlt.character(as.character(x), ...) :
  character string is not in a standard unambiguous format

On Sat, Dec 31, 2016 at 10:36 AM, Bert Gunter <bgunter.4567 at gmail.com>
wrote:

> ?substring
>
> (among others)
>
> -- Bert
> Bert Gunter
>
> "The trouble with having an open mind is that people keep coming along
> and sticking things into it."
> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>
>
> On Sat, Dec 31, 2016 at 9:26 AM, lily li <chocold12 at gmail.com> wrote:
> > Hi all,
> >
> > Thanks for your help. Now I can convert data to the format "yyyy-mm-dd
> > hh:mm:ss", but how to convert it to "yyyy-mm-dd"? The datasets are txt
> > files, not from excel.
> >
> > On Fri, Dec 30, 2016 at 3:01 PM, Duncan Mackay <dulcalma at bigpond.com>
> wrote:
> >
> >> Hi
> >>
> >> Is this the output from Excel?
> >> If so format it in Excel for a date format not a date-time format .
> >> Depending how the dates were inputted into Excel and the Excel setup a
> date
> >> may not be a date format.
> >> There are no rules with microsoft formatting so beware!
> >>
> >>
> >> Regards
> >>
> >> Duncan
> >>
> >> Duncan Mackay
> >> Department of Agronomy and Soil Science
> >> University of New England
> >> Armidale NSW 2351
> >> Email: home: mackay at northnet.com.au
> >>
> >> -----Original Message-----
> >> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of lily li
> >> Sent: Saturday, 31 December 2016 05:38
> >> To: Rui Barradas
> >> Cc: R mailing list
> >> Subject: Re: [R] about data format in R
> >>
> >> Hi Rui,
> >>
> >> Thanks for your reply. When I read in data using my code, the first
> column
> >> ranges from 0 to 1. So when I use the code you wrote, it shows the error
> >> message:
> >> Error in as.POSIXct.numeric(DF$Date, format = "%m/%d/%Y-%H:%M:%S") :
> >> 'origin' must be supplied
> >>
> >>
> >> On Fri, Dec 30, 2016 at 11:23 AM, Rui Barradas <ruipbarradas at sapo.pt>
> >> wrote:
> >>
> >> > Hello,
> >> >
> >> > Have you tried
> >> >
> >> > df$date <- as.POSIXct(dat$date, format = "%m/%d/%Y-%H:%M:%S")
> >> >
> >> > ?
> >> >
> >> > Hope this helps,
> >> >
> >> > Rui Barradas
> >> >
> >> >
> >> >
> >> > Em 30-12-2016 17:40, lily li escreveu:
> >> >
> >> >> Hi R users,
> >> >>
> >> >> I'm trying to read in data, and then plot time series data. However,
> I
> >> >> have
> >> >> some problems. In my dataset, the first column represents time, and
> in
> >> the
> >> >> format:
> >> >> mm/dd/yyyy-hr:min:sec; For example, 10/01/1995-00:00:00,
> >> >> 10/01/1995-06:00:00, etc.
> >> >>
> >> >> df:
> >> >>             date                    evap     precip    intercept
> >> >> 10/01/1995-00:00:00       1.5          2            0.2
> >> >> 10/01/1995-12:00:00       1.7          2.2         0.1
> >> >> 10/02/1995-00:00:00       1.5          1.8         0.3
> >> >> ...
> >> >>
> >> >> My code is like this
> >> >> file1 = read.table('df', head=T)
> >> >>
> >> >> When I read in data, I found that it read incorrectly. How to format
> >> when
> >> >> read in data? Thanks.
> >> >>
> >> >>         [[alternative HTML version deleted]]
> >> >>
> >> >> ______________________________________________
> >> >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >> >> https://stat.ethz.ch/mailman/listinfo/r-help
> >> >> PLEASE do read the posting guide http://www.R-project.org/posti
> >> >> ng-guide.html
> >> >> and provide commented, minimal, self-contained, reproducible code.
> >> >>
> >> >>
> >>
> >>         [[alternative HTML version deleted]]
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >> 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.
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >> 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.
> >>
> >
> >         [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > 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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