aggregate
maybe you could use something like this:
dat <- data.frame(id = rep(1:3, 3), date = as.Date(rep(c("2005-08-25",
"2005-08-26", "2005-08-29"), each = 3)))
########################
do.call("rbind", lapply(split(dat, dat$id), function(x) data.frame(id
= x$id[1], start = min(x$date), end = max(x$date))))
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: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.be/biostat/
http://www.student.kuleuven.be/~m0390867/dimitris.htm
----- Original Message -----
From: "Omar Lakkis" <uofiowa at gmail.com>
To: <r-help at stat.math.ethz.ch>
Sent: Tuesday, August 30, 2005 4:36 PM
Subject: [R] aggregate
How can I aggregate this data.frame to list the min and max date for each unique id?
From this :
r = data.frame(id=rep(seq(1:3), 3), date=
as.Date(c(rep("2005-08-25",3), rep("2005-08-26",3),
rep("2005-08-29", 3)), "%Y-%m-%d"))
r
id date 1 2005-08-25 2 2005-08-25 3 2005-08-25 1 2005-08-26 2 2005-08-26 3 2005-08-26 1 2005-08-29 2 2005-08-29 3 2005-08-29 I want to get to this:
id start end 1 2005-08-25 2005-08-29 2 2005-08-25 2005-08-29 3 2005-08-25 2005-08-29 I tried aggregate and aggregate.data.frame but the date column keeps getting converted into a number.
______________________________________________ R-help at stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html