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st: RE: how to generate lates nonmissing lagged value


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: how to generate lates nonmissing lagged value
Date   Fri, 4 Jul 2003 19:24:27 +0100

olena-stavrunova@uiowa.edu

> I have a panel dataset with missing values and for each 
> individual at each 
> time period I need to generate variable V1 which assumes 
> value of 1 if current 
> and latest nonmissing lagged value of another variable V2 
> =1 and is zero or 
> missing otheriwse.
> Could you, please, give me a hint on how to do this.

Panel data: I assume variables -id- and -time-, so 
the latest previous non-missing value of -v2- is 
given by 

gen prevv2 = . 

bysort id (time) : 
	replace prevv2 = 
		cond(v2[_n-1] < ., v2[_n-1], prevv2[_n-1]) 

Then you appear to have a double condition 

(a) current value of v2 is 1 
(b) latest nonmissing lagged value of v2 is 1 

which is made into an indicator by 

gen v1 = v2 == 1 & prevv2 == 1 

There is related background at 

How can I replace missing values with previous 
or following nonmissing values?
http://www.stata.com/support/faqs/data/missing.html

latest, London, 4 July 2003: George III says sorry... 

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