[R] Time format lagging issue

[William Dunlap]

That
  tmp1 - 30*60
can also be done as
  tmp1 - as.difftime(30, units="mins")
so you don't have to remember that the internal representation of POSIXct
is seconds since the start of 1970.  You can choose from the following
equivalent expressions.
  tmp1 - as.difftime(0.5, units="hours")
  tmp1 - as.difftime(1/2 * 1/24, units="days")
  tmp1 - as.difftime(30*60, units="secs")
  tmp1 - as.difftime(1/2 * 1/24 * 1/7, units="weeks")


Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Wed, Aug 31, 2016 at 2:44 PM, MacQueen, Don <macqueen1 at llnl.gov> wrote:

> Try following this example:
>
> mydf <- data.frame(t1=c('201112312230', '201112312330'))
> tmp1 <- as.POSIXct(mydf$t1, format='%Y%m%d%H%M')
> tmp2 <- tmp1 - 30*60
> mydf$t2 <- format(tmp2, '%Y%m%d%H%M')
>
> It can be made into a single line, but I used intermediate variables tmp1
> and tmp2 so that it would be easier to follow.
>
> Base R is more than adequate for this task.
>
> Please get rid of the asterisks in your next email. The just get in the
> way. Learn how to send plain text email, not HTML email. Please.
>
>
>
>
> --
> Don MacQueen
>
> Lawrence Livermore National Laboratory
> 7000 East Ave., L-627
> Livermore, CA 94550
> 925-423-1062
>
>
>
>
>
> On 8/31/16, 9:07 AM, "R-help on behalf of Bhaskar Mitra"
> <r-help-bounces at r-project.org on behalf of bhaskar.kolkata at gmail.com>
> wrote:
>
> >Hello Everyone,
> >
> >I am trying a shift the time series in a dataframe (df) by 30 minutes . My
> >current format looks something like this :
> >
> >
> >
> >*df$$Time 1*
> >
> >
> >*201112312230*
> >
> >*201112312300*
> >
> >*201112312330*
> >
> >
> >
> >*I am trying to add an additional column of time (df$Time 2) next to  Time
> >1 by lagging it by ­ 30minutes. Something like this :*
> >
> >
> >*df$Time1                   **df$$Time2*
> >
> >
> >*201112312230          **201112312200*
> >
> >*201112312300          **201112312230*
> >
> >*201112312330          **201112312300*
> >
> >*201112312330          *
> >
> >
> >
> >
> >
> >*Based on some of the suggestions available, I have tried this option *
> >
> >
> >
> >*require(zoo)*
> >
> >*df1$Time2  <- lag(df1$Time1, -1, na.pad = TRUE)*
> >
> >*View(df1)*
> >
> >
> >
> >*This does not however give me the desired result. I would appreciate any
> >suggestions/advice in this regard.*
> >
> >
> >*Thanks,*
> >
> >*Bhaskar*
> >
> >       [[alternative HTML version deleted]]
> >
> >______________________________________________
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> >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.
>

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