Patrick,
my intention was, to perform a one-to-one exact match, which pairs each treated
unit with ONE control unit (without replacement), using my two confounders
(age, school) for matching.
Patrick Connolly schrieb:
On Mon, 14-Apr-2008 at 08:37AM +0200, Udo wrote:
|> Zitat von Peter Alspach <[EMAIL PROTECTED]>:
|>
|> > Udo
|> >
|> > Seems you might want merge()
|> >
|> > HTH .......
|> >
|> > Peter Alspach
|>
|> Thank you Peter and Jorge,
|>
|> but as I had written in my last sentence,
|> "Merge doesn´t do the job, because it makes
|> all possible matches", but maybe there is a sophisticated
|> solution with "merge", I could not bring light to.
>Maybe it would help if we knew what you mean by 'all' in this context.
>To get the NAs in your example, it is NECESSARY to use the all = TRUE
>argument. Without the all = TRUE, the NA rows are omitted.
With 'all' I mean, that in the merged data frame (13 Obs) there are 8 cases
(2*4) with age=1 and school=10 (all possible combinations).
>What is it that you don't want in this:
I only "need" line 1, 6 and 9. To show this,
I added "needed" by hand.
age school out1 out2 needed
1 1 10 9.5 1.1 yes
2 1 10 9.5 2.0 no
3 1 10 9.5 3.5 no
4 1 10 9.5 4.9 no
5 1 10 2.3 1.1 no
6 1 10 2.3 2.0 yes
7 1 10 2.3 3.5 no
8 1 10 2.3 4.9 no
9 2 20 3.3 6.5 yes
10 2 20 4.1 6.5 no
11 2 20 5.9 6.5 no
12 3 33 NA 5.2 no
13 4 11 4.6 NA no
>Whatever it is, can't you subset them out?
Yes, that´s the problem. To describe what I mean, I added the variable needed
by hand. I don´t know how to compute such a variable to subset.
My final data frame should look like this:
age school out1 out2 nedded
1 1 10 9.5 1.1 yes
6 1 10 2.3 2.0 yes
9 2 20 3.3 6.5 yes
I hope, I could make clear, what the problem ist and waht I mean.
An alternative would be using packages like Matching or MatchIt, which need
a long data structure with one data frame and not a wide one with two data
frames.
Many thanks!
Udo
______________________________________________
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.
