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Re: st: Merging longitudinal data set
From
Abdel Rahmen El Lahga <[email protected]>
To
[email protected]
Subject
Re: st: Merging longitudinal data set
Date
Fri, 16 Jul 2010 23:11:54 +0100
I think that your strategy is wrong. When you have a panel data (each
wave in a separate file) I suggest th command "append" instead of
"merge".
"append" will concatunate vertically your waves and the final data set
could be analyzed as panel. I presule that you have a variable year
identifying tha wave date. If not you should create such variable
before appending file.
Before further analysis see the commands "xtset" "xtdes"...:)
AbdelRahmen
2010/7/16 Andreas Jensen <[email protected]>:
> 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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--
AbdelRahmen El Lahga
*
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