Message-ID: <A5923CD5-58C2-4804-9AC4-B9A539DAFC5C@comcast.net>
Date: 2009-11-16T19:53:18Z
From: David Winsemius
Subject: extracting the last row of each group in a data frame
In-Reply-To: <6e9bb1ed91068f2ef02f2b705c0fd05f.squirrel@webmail.andrew.cmu.edu>
On Nov 16, 2009, at 2:42 PM, Hao Cen wrote:
> 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
>
by(dfname$Value, dfname$Name, tail, 1) #which gets you a list
Or:
aggregate(dfname$Value, list(dfname$Name), tail, 1) #which returns a
data.frame
Group.1 x
1 A 3
2 B 8
3 C 2
4 D 3
> I would like to get a data frame as
> Name Value
> A 3
> B 8
> C 2
> D 3
>
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT