I usually use the following function:
last.record <- function(data, id, ..., na.last=TRUE, decreasing=FALSE){
#*** Make vector of variables to sort by
v <- c(id, unlist(list(...)))
#*** Sort Data Frame
data <- data[do.call(order,
c(data[,v, drop=FALSE], na.last=na.last,
decreasing=decreasing)),]
#*** Extract last record for each id
data[!duplicated(data[,id], fromLast=TRUE),]
}
Data Data Frame from which the record is to be extracted
Id ID variable from which the record is to be extracted. The
data frame is automatically
sorted by this variable. May be either a character string
or an integer.
... Names of variables (or indices) in additon to id by which
data should be sorted.
na.last Argument passed to order(). Determines if missing values
are placed at the end
of the sorting.
Decreasing Argument passed to order(). Determines if data frame is
sorted in descending
order.
So, in your example
> df <- data.frame(Name = c("A", "A", "A", "B", "B", "C", "D"),
Value = c(1, 2, 3, 4, 8, 2, 3))
> last.record(df, "Name", "Value")
> last.record(df, 1, 2)
-----Original Message-----
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org]
On Behalf Of Hao Cen
Sent: Monday, November 16, 2009 2:43 PM
To: r-help@r-project.org
Subject: [R] extracting the last row of each group in a data frame
Hi,
I would like to extract the last row of each group in a data frame.
The data frame is as follows
Name Value
A 1
A 2
A 3
B 4
B 8
C 2
D 3
I would like to get a data frame as
Name Value
A 3
B 8
C 2
D 3
Thank you for your suggestions in advance
Jeff
______________________________________________
R-help@r-project.org 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.
===================================
P Please consider the environment before printing this e-mail
Cleveland Clinic is ranked one of the top hospitals
in America by U.S.News & World Report (2009).
Visit us online at http://www.clevelandclinic.org for
a complete listing of our services, staff and
locations.
Confidentiality Note: This message is intended for use\...{{dropped:13}}
______________________________________________
R-help@r-project.org 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.
