try this:
dat <- read.table(textConnection(
"Id Year
123456 2001
123456 2002
123456 2003
655432 2001
655432 2002
655432 2003"), header = TRUE)
closeAllConnections()
dat[!duplicated(dat$Id), ]
# or
dat[tapply(row.names(dat), dat$Id, head, 1), ]
I hope it helps.
Best,
Dimitris
----
Dimitris Rizopoulos
Biostatistical Centre
School of Public Health
Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
http://www.student.kuleuven.be/~m0390867/dimitris.htm
----- Original Message -----
From: "Jojje Andersson" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Friday, May 30, 2008 9:13 AM
Subject: [R] Aggregate by First case
Hello!
I have an maybe a to a simple question but I cant get it right.
I have a dataframe with in one column an id-variable and in another
a year-variable. One id-number can occur several years.
I have sorted the dataframe on id then on year so the same id-number
is sorted by year with the first occurens at top.
Now I want to make a subset of this dataframe with just the first
year the id-number occur, so the first case of every id.
Id Year
123456 2001
123456 2002
123456 2003
655432 2001
655432 2002
655432 2003
Is there a simple command I can do?
Thanks!
Jojje
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