On Mar 21, 2011, at 3:38 PM, Roberto Lodeiro Muller wrote:
-----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
dat$dt <- as.Date(dat$DATE, format="%d-%b-%y")
dat$diffdt <- c(diff(dat$dt), NA)
dat$diffRES <- c(diff(dat$RES), NA)
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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