Roberto,
There are duplicate commands already written for Stata, run help
duplicates.
The following link has also come in handy for me in the past if you are
looking to count the recurrence of a particular individual across time.
Your issue of consecutive years would require the code offered here to
be tweaked a bit.
http://www.stata.co.uk/support/faqs/data/dups.html
Carter
************************************
Carter Rees, M.A.
Email: [email protected]
************************************
-----Original Message-----
From: Roberto [mailto:[email protected]]
Sent: Monday, October 11, 2004 6:35 AM
To: [email protected]
Subject: st: Data manipulation: how to keep only consecutive obs in an
unbalanced panel
Dear Statalist friends
I am currently trying to run a GMM estimation using the xtabond2
command.
I have an unbalanced panel so I would want to manipulate my dataset in a
way that Stata only keeps the continuous observations for each firm For
example consider these 3 firms
code name year run maxrun _spell _seq _end
n
N
135540 A 1995 1 5 1 1 1
1
6
135540 A 1997 1 5 2 1 0 2
6
135540 A 1998 2 5 2 2 0 3
6
135540 A 1999 3 5 2 3 0 4
6
135540 A 2000 4 5 2 4 0 5
6
135540 A 2001 5 5 2 5 1 6
6
900327 B 1991 1 7 1 1 0 1
10
900327 B 1992 2 7 1 2 0 2
10
900327 B 1993 3 7 1 3 1 3
10
900327 B 1995 1 7 2 1 0 4
10
900327 B 1996 2 7 2 2 0 5
10
900327 B 1997 3 7 2 3 0 6
10
900327 B 1998 4 7 2 4 0 7
10
900327 B 1999 5 7 2 5 0 8
10
900327 B 2000 6 7 2 6 0 9
10
900327 B 2001 7 7 2 7 1 10
10
134982
C 1997 1 1 1 1 1 1 3
134982 C 1999 1 1 2 1 1 2
3
134982 C 2001 1 1 3 1 1 3
3
with the tsspell command I have been able to identify the maximum number
of consecutive observations per firms.
The problem is that if I write
keep if maxrun>=5
stata only drops firm "C" whereas I would want it to drop all the
non-consecutive observations in all panels so that the database would
look
like:
code name year
135540 A 1997
135540 A 1998
135540 A 1999
135540 A 2000
135540 A 2001
900327 B 1995
900327 B 1996
900327 B 1997
900327 B 1998
900327 B 1999
900327 B 2000
900327 B 2001
Can anyone help?
Thank you all for the kind attention.
Best Regards
Roberto Mura
PhD candidate
University of York
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