you can use the following (based on Gabor's answer):
math <- c(80,75,70,65,65,70)
reading <- c(65,70,88,NA,90,NA)
id <- c('001','001','001','002','003','003')
score <- data.frame(id, reading, math)
#############
# it might be useful to sort first
# score <- score[order(score$id), ]
score
score[unlist(tapply(row.names(score), score$id, tail, n = 2)), ]
look at ?tail() for more info.
I hope it helps.
Best,
Dimitris
----
Dimitris Rizopoulos
Ph.D. Student
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: "Lauri Nikkinen" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, March 20, 2007 3:33 PM
Subject: [R] Select the last two rows by id group
> Hi R-users,
>
> Following this post
> http://tolstoy.newcastle.edu.au/R/help/06/06/28965.html ,
> how do I get last two rows (or six or ten) by id group out of the
> data
> frame? Here the example gives just the last row.
>
> Sincere thanks,
> Lauri
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> [email protected] mailing list
> 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.
>
Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm
______________________________________________
[email protected] mailing list
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.
