Nick, Michael,
Thanks for both your feedback.
The code is exactly what I was trying to achieve.
- Tom
______________________
Thomas Erdmann
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79594 Inzlingen
Germany
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[email protected]
-----Urspr�ngliche Nachricht-----
Von: [email protected]
[mailto:[email protected]] Im Auftrag von Michael Blasnik
Gesendet: Donnerstag, 7. Dezember 2006 19:26
An: [email protected]
Betreff: st: Re: Repeating values
...
I think this will do what you want (assuming that you also have a variable
named company in your dataset):
gsort company -year
by company: gen todrop=sum(Var1==Var1[1] & Var1==Var1[_n+1])
by company: replace Var1=. if todrop=_n
drop todrop
The data are sorted in reverse time (as Nick mentioned) and then todrop is
created as a counter for the cumulative number of observations equal to the
first (final timewise) observation and also equal to the next observation
(prior timewise). Then, if the observation number equals todrop, it should
be changed to missing.
Michael Blasnik
----- Original Message -----
From: "Thomas Erdmann" <[email protected]>
To: <[email protected]>
Sent: Thursday, December 07, 2006 11:56 AM
Subject: st: Repeating values
> Hi,
>
> I am working with some variables that or "wrong" in the sense that if one
> share was taken off the market (i.e. the company was dissolved), the last
> value of the variable is repeated instead of containing missing values.
>
> e.g.
>
> Status Year Var1
> Listed 1991 0.9
> Listed 1992 0.95
> Listed 1993 0.93
> Delisted 1994 0.93
> Delisted 1995 0.93
> ..
> Delisted 2006 0.93 (value is always repeated up to present time)
>
> Whereas years 1994-2006 should contain missing values. I came up with this
> cleaning process:
>
> foreach X of varlist var1 var2 var3 {
> generate `X'new=`X'
> replace `X'new=. if `X'==L.`X'
> replace `X'=`X'new
> drop `X'new
> }
>
> Which is okay, but also sets the value to missing if one observation for a
> listed company repeats, so it also deletes observations that would be
> fine.
>
> Any suggestions on how I can only replace the "wrong" values?
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