[R] how to select the first observation only?

[Daniel Malter]

Gallon, your question looks very homeworky. People on this list are not
likely to help you unless you can demonstrate own effort (even if it
failed), and the list is not for homework questions in case it is one. Where
exactly are you stuck?

Daniel

-------------------------
cuncta stricte discussurus
-------------------------

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of gallon li
Sent: Wednesday, April 21, 2010 10:18 PM
To: r-help
Subject: [R] how to select the first observation only?

Dear r-helpers,

I have a very simple question. Suppose my data is like

id=c(rep(1,2),rep(2,2))
b=c(2,3,4,5)
m=cbind(id,b)

> m
     id b
[1,]  1 2
[2,]  1 3
[3,]  2 4
[4,]  2 5
I wish to select the first observation for each id. That is, I want to
quickly select two rows:

id b
1 2
2 4

only. how should i do this?

	[[alternative HTML version deleted]]

______________________________________________
R-help at 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.