-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Morway,
Eric
Sent: Thursday, May 26, 2016 5:00 PM
To: R mailing list
Subject: [R] rollapply and difftime
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]))
}
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