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st: Merging longitudinal data set
From
Andreas Jensen <[email protected]>
To
[email protected]
Subject
st: Merging longitudinal data set
Date
Fri, 16 Jul 2010 23:59:40 +0200
Hi Statalist.
I'm a new Stata user (previously only used R) and I'm working on a
project involving a longitudinal data set. There are two waves each
contained in its own data file and there is a common ID variable which
is consistent among the waves. I'm trying to wrap my head around the
merge command and I'm sure this is a fairly basic question. I,
however, would appreciate some confirmation on that what I'm doing is
hopefully correct.
What I'm troubled about is that there are people from wave 1 that has
dropped out when wave 2 was conducted (their ID does not exist in the
wave 2 data file), and there has been added additional people in wave
2 that aren't present in wave 1 (their ID does not exist in the wave 1
data file).
I have sorted each data file according to the ID variable and then
executed a merge 1:1 on the ID with wave 1 as master. I get the
following output.
Result # of obs.
-----------------------------------------
not matched 28,046
from master 12,373 (_merge==1)
from using 15,673 (_merge==2)
matched 18,742 (_merge==3)
-----------------------------------------
So assuming that my command is correct, is it then true that there are
18742 individuals in both waves, 12373 individuals which has dropped
out after wave 1 and 15673 individuals that have been added in wave 2?
Thanks in advance,
Andreas Jensen
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