(mods: can you un-flag me if I am still flagged?)
Hi,
First, I would convert the DATE column to an integer. I found this by
quick googling, perhaps as.Date is your weapon of choice:
https://stat.ethz.ch/pipermail/r-help/2008-August/169870.html
For the column generation I think you will have to use a for-loop here:
yourdata$ResultDiff <- 0
yourdata$DateDiff <- 0
for( i in 1:nrow(yourdata) ){
yourdata$ResultDiff[i] <- yourdata$RESULT[i] - yourdata$RESULT[i+1] #
should automatically NA the last cell
yourdata$DateDiff[i] <- yourdata$datenumber[i] -
yourdata$datenumber[i+1]
}
where datenumber is your integer column of the date.
-- Alex
Am 21.03.2011 20:38, schrieb Roberto Lodeiro Muller:
-----Original Message-----
From: Roberto Lodeiro Muller<roberto.mul...@doctor.com>
To: roberto.mul...@doctor.com
Sent: Mon, Mar 21, 2011 3:37 pm
Subject: Re: [R] Computing row differences in new columns
Sorry, my data appeared badly formatted to me, so I converted it to plain text:
And just to clarify, for each subject in the first row it should appear the
difference to the next row, so that the last entry on each subject would be a
NA.
Thanks again for your help
Roberto
SUBJECT DATE RESULT DateDiff ResultDiff
10751 22-Jul-03 3.5
10751 13-Feb-04 1.3
10751 20-Aug-04 1.6
10751 08-Mar-05 1.7
10751 30-Aug-05 1.6
10751 21-Feb-06 1.3
10751 31-Aug-06 1.2
10751 27-Feb-07 1.5
10751 29-Aug-07 1
10752 29-Jul-03 5.9
10752 24-Feb-04 5
10752 25-Aug-04 3.6
10752 11-Mar-05 5.1
10752 18-Sep-05 2.2
10752 23-Feb-06 3.1
10752 24-Aug-06 3.7
10752 27-Feb-07 6
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