clear
input id year
4 1987
4 1993
4 1994
9 1986
9 1987
9 1988
9 1989
9 1990
9 1992
9 1993
9 1994
9 1995
9 1996
9 1997
end
bysort id (year): gen tag = 1 if _n ==1
bysort id (year): replace tag = 1 if mod(year, 3) ==1 & tag == . &
tag[_n-1] != 1
keep if tag ==1
drop tag
l, sepby(id)
gives me
id year
4 1987
9 1986
9 1990
9 1993
9 1996
It dosent keep the year 1993 for id 4
Thanks
rajesh
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Scott Merryman
Sent: 19 May 2008 02:50
To: [email protected]
Subject: Re: st: keeping dates which are n periods apart
Does this work?
clear
input id year
4 1987
4 1988
4 1989
4 1990
4 1992
4 1993
4 1994
9 1986
9 1987
9 1988
9 1989
9 1990
9 1992
9 1993
9 1994
9 1995
9 1996
9 1997
end
bysort id (year): gen tag = 1 if _n ==1
bysort id (year): replace tag = 1 if mod(year, 3) ==1 & tag == . &
tag[_n-1] != 1
keep if tag ==1
drop tag
l, sepby(id)
Scott
On Sun, May 18, 2008 at 8:02 PM, Rajesh Tharyan <[email protected]>
wrote:
> Hi all,
>
> I have this ( a subset of the original dataset, the original dataset has
> about 6000 ids with an average of 6 years each)
>
> id year
> 4 1987
> 4 1988
> 4 1989
> 4 1990
> 4 1992
> 4 1993
> 4 1994
> 9 1987
> 9 1988
> 9 1989
> 9 1990
> 9 1992
> 9 1993
> 9 1994
>
> I need to keep years if they are more than 2 years apart by company.
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