Hi Stefano,
You certainly did help; it worked perfectly. And your description of the
type of object I'm dealing with spurred me to inform myself on lists, an
item I previously ignored having fixated on data frames. Thank you.
Charlie
-----Original Message-----
From: stefano iacus [mailto:stefano.iacus@unimi.it]
Sent: Wednesday, July 22, 2009 3:56 PM
To: Abromaitis, Charlie
Cc: cem(a)lists.gking.harvard.edu; Gary King
Subject: Re: [cem] Extracting Matched Data Set in cem
Hi Charles,
the output of the cem function returns an object with several slots.
In particular, $matched is a boolean vector for matched/unmatched units.
Here is an example of use
library(cem)
data(LL)
dim(LL)
[1] 722 12
mat <- cem("treated", LL,
drop="re78")
mat
G0 G1
All 425 297
Matched 222 163
Unmatched 203 134
LLmatched <- LL[mat$matched,]
dim(LLmatched)
[1] 385 12
hope this helps
stefano
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