[R] rollapply and difftime

[Jeff Newmiller]

What about just

diff( dts )

or

as.numeric( diff( dts ), units="days" )

?
-- 
Sent from my phone. Please excuse my brevity.

On May 26, 2016 5:09:20 PM PDT, "MacQueen, Don" <macqueen1 at llnl.gov> wrote:
>You want the number of days between dates?
>Does this do the trick?
>
>dts <- Sys.Date()+ c(1,2,3,5,6,9)
>dts[-1] - dts[-length(dts)]
>
>Time differences in days
>[1] 1 1 2 1 3
>
>
>
>-- 
>Don MacQueen
>
>Lawrence Livermore National Laboratory
>7000 East Ave., L-627
>Livermore, CA 94550
>925-423-1062
>
>
>
>
>
>On 5/26/16, 4:59 PM, "R-help on behalf of Morway, Eric"
><r-help-bounces at r-project.org on behalf of emorway at usgs.gov> wrote:
>
>>Technically, the code below works and results in a column that I'm
>>interested in working with for further processing.  However, it is
>both
>>inefficient on lengthy (>100 yr) daily time series and is, frankly,
>not
>>the
>>R way of doing things.  Using the 'Daily' data.frame provided below,
>I'm
>>interested to know the propeR way of accomplishing this same task in
>an
>>efficient manner.  I tried combinations of rollapply and difftime, but
>was
>>unsuccessful.  Eric
>>
>>Daily <- read.table(textConnection("     Date        Q
>>1911-04-01 4.530695
>>1911-04-02 4.700596
>>1911-04-03 4.898814
>>1911-04-04 5.097032
>>1911-04-05 5.295250
>>1911-04-06 6.569508
>>1911-04-07 5.861587
>>1911-04-08 5.153666
>>1911-04-09 4.445745
>>1911-04-10 3.737824
>>1911-04-11 3.001586
>>1911-04-12 3.001586
>>1911-04-13 2.350298
>>1911-04-14 2.661784
>>1911-04-16 3.001586
>>1911-04-17 2.661784
>>1911-04-19 2.661784
>>1911-04-28 3.369705
>>1911-04-29 3.001586
>>1911-05-20 2.661784"),header=TRUE)
>>
>>Daily$Date <- as.Date(Daily$Date)
>>Daily$tmdiff <- NA
>>for(i in seq(2,length(Daily$Date),by=1)){
>>  Daily$tmdiff[i] <-
>as.numeric(difftime(Daily$Date[i],Daily$Date[i-1]))
>>}
>>
>>	[[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.

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