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st: Re: creating a "years since event" variable in panel data
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From |
"Sergiy Radyakin" <[email protected]> |
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To |
<[email protected]> |
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Subject |
st: Re: creating a "years since event" variable in panel data |
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Date |
Thu, 8 Mar 2007 20:51:22 +0100 |
Hello Christer,
I assume you have data in the following form:
. l ,sepby(id)
+-------------------+
id year event
-------------------
1. 1 1997 0
2. 1 1998 0
3. 1 1999 1
4. 1 2000 0
5. 1 2001 0
6. 1 2002 1
7. 1 2003 0
8. 1 2004 0
-------------------
9. 2 1997 1
10. 2 1998 1
11. 2 1999 1
12. 2 2000 0
13. 2 2001 0
14. 2 2002 0
15. 2 2003 0
16. 2 2004 0
-------------------
17. 3 1997 0
18. 3 1998 0
19. 3 1999 0
20. 3 2000 0
21. 3 2001 0
22. 3 2002 1
+-------------------+
(Namely, I don't understand what you mean by time ranging from 0 to 7)
Type:
gen d=.
bys id (year): replace d=cond(event==1,0,d[_n-1]+1)
l ,sepby(id)
Which results in the following:
+-----------------------+
id year event d
-----------------------
1. 1 1997 0 .
2. 1 1998 0 .
3. 1 1999 1 0
4. 1 2000 0 1
5. 1 2001 0 2
6. 1 2002 1 0
7. 1 2003 0 1
8. 1 2004 0 2
-----------------------
9. 2 1997 1 0
10. 2 1998 1 0
11. 2 1999 1 0
12. 2 2000 0 1
13. 2 2001 0 2
14. 2 2002 0 3
15. 2 2003 0 4
16. 2 2004 0 5
-----------------------
17. 3 1997 0 .
18. 3 1998 0 .
19. 3 1999 0 .
20. 3 2000 0 .
21. 3 2001 0 .
22. 3 2002 1 0
+-----------------------+
Notice that in this version it is "duration since the most recent occurance
of the event". Alternatively it can be "duration since the first occurance
of the event".
First is reasonable if your event is "got a new job" -- then d is tenure.
Alternatively, if your event is something like "a child is born", -- then dd
might be "duration of life with children" (though no account is given for
possible move-outs). Then one will need to change the program:
gen dd=.
bys id (year): replace dd=cond(dd[_n-1]==.,cond(event==1,0,.),dd[_n-1]+1)
+----------------------------+
id year event d dd
----------------------------
1. 1 1997 0 . .
2. 1 1998 0 . .
3. 1 1999 1 0 0
4. 1 2000 0 1 1
5. 1 2001 0 2 2
6. 1 2002 1 0 3
7. 1 2003 0 1 4
8. 1 2004 0 2 5
----------------------------
9. 2 1997 1 0 0
10. 2 1998 1 0 1
11. 2 1999 1 0 2
12. 2 2000 0 1 3
13. 2 2001 0 2 4
14. 2 2002 0 3 5
15. 2 2003 0 4 6
16. 2 2004 0 5 7
----------------------------
17. 3 1997 0 . .
18. 3 1998 0 . .
19. 3 1999 0 . .
20. 3 2000 0 . .
21. 3 2001 0 . .
22. 3 2002 1 0 0
+----------------------------+
Best regards,
Sergiy Radyakin
----- Original Message -----
From: "Christer Thrane" <[email protected]>
To: <[email protected]>
Sent: Thursday, March 08, 2007 7:23 PM
Subject: st: creating a "years since event" variable in panel data
Hi,
I have a annual panel data set (1 obs per year), where ID identifies the
person and the variable OBSYEAR the year of observation (1995=1, 1996=2,
..., 2002=7).
The variable TIME is the time dimension, ranging from 0 to 7.
The variable EVENT is a dymmy (1=event happened during the year in
question; 0=event did not happen during the year in question).
Q: How do I create the variable NUMBER OF YEARS SINCE (A POSSIBLE) CHANGE
FROM 0 to 1 on EVENT?
Best regards,
Christer Thrane
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