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st: RE: Merge problem
From
Joe Canner <[email protected]>
To
"[email protected]" <[email protected]>
Subject
st: RE: Merge problem
Date
Fri, 4 Oct 2013 11:56:06 +0000
Erik,
If there are a fixed, known number of periods per year, you can use -expand- in dataset (A). Suppose (as in your example) there are 4 periods (1,2,3,4):
. expand 3
. bys year firm_id: gen period_id=_n
However, if the number of periods depends on some information in dataset (B), that's a different story. If so, please provide more information on how the number of periods is to be determined.
Regards,
Joe Canner
Johns Hopkins University School of Medicine
________________________________________
From: [email protected] [[email protected]] on behalf of Erik Aadland [[email protected]]
Sent: Friday, October 04, 2013 4:18 AM
To: [email protected]
Subject: st: Merge problem
Dear Statalist.
I have two datasets. One dataset (A) contains the variables "year" and "firm_id". A firm observation ("firm_id") occurs only once in a given "year".
The other dataset (B) contains the variables "year", "period_id" and "firm_id". There are many periods within a given year, and firm observations ("firm_id") are nested within periods. So a given firm ("firm_id") may occur several times in a given year. The firms in (A) are not the same firms as in (B). The structure of (A) and (B) are as follows.
(A):
year firm_id
2003 1
2003 2
2003 3
2003 4
2004 1
2004 2
2004 5
2004 6
(B):
year period_id firm_id
2003 1 11
2003 1 12
2003 2 13
2003 2 14
2003 2 11
2004 3 11
2004 3 12
2004 3 15
2004 4 16
2004 4 17
I want to merge the firms in (A) into (B) such that the firms in (A) in a given year occur in all periods for the corresponding year in (B). The problem is that I don't have "period_id" for my firm observations in (A).
Is there a smart way to handle this problem? I use Stata 12.
Any input on this would be much appreciated.
Sincerely,
Erik
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