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Re: st: RE: Quick Question on how to drop individualobservations


From   JEFFREY ROSEN <rosen.53@osu.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: Quick Question on how to drop individualobservations
Date   Fri, 16 Jun 2006 14:01:09 -0400

Thanks for the reply. This is exactly what I needed. I have one more slightly related question. 

Suppose I have a data set such as:

obs 1 hhold 1 rd 1 income 5
obs 2 hhold 1 rd 2 income 10
obs 3 hhold 1 rd 3 income 6
obs 4 hhold 2 rd 1 income 10
obs 5 hhold 2 rd 2 income 10
obs 5 hhold 2 rd 3 income 12

I want to find the change in income across each round.

So, I would like to create a variable incomedifference
where:

obs 1: incomedifference = 0
obs 2: incomedifference = 5 (10 - 5 = 5)
obs 3: incomedifference = -4 (6 - 10 = -4)
obs 4: incomedifference = 0
obs 5: incomedifference = 0
obs 6: incomedifference = 2

Thanks in advance,

Jeff


----- Original Message -----
From: Michael Blasnik <michael.blasnik@verizon.net>
Date: Friday, June 16, 2006 1:28 pm
Subject: Re: st: RE: Quick Question on how to drop individual observations

> Your original query was ambiguous.  The solution is now simpler:
> 
> bysort hhold rd: drop if _n==1 & _n<_N
> 
> will drop the first observation if there are duplicates on hhold 
> and rd.  If 
> you only want to keep the last observation (in case there are 
> triplets or 
> more) then:
> 
> bysort hhold rd: keep if _n==_N
> 
> Michael Blasnik
> michael.blasnik@verizon.net
> 
> ----- Original Message ----- 
> From: "JEFFREY ROSEN" <rosen.53@osu.edu>
> To: <statalist@hsphsun2.harvard.edu>
> Sent: Friday, June 16, 2006 12:44 PM
> Subject: Re: st: RE: Quick Question on how to drop individual 
> observations
> 
> > Thanks for the quick reply. Unfortunately, the code didn't work 
> as I had 
> > hoped.
> >
> > The dataset is drawn up as:
> >
> > obs 1 hhold 1 rd 1
> > obs 2 hhold 1 rd 2
> > obs 3 hhold 1 rd 2
> > obs 4 hhold 1 rd 3
> >
> > The code below will drop the observation where the hhold value 
> and the rd 
> > value are the same. So in the above example, hhold = rd = 1 at 
> observation 
> > 1. Observation 1 was dropped. What I would like is to drop 
> observation 2 
> > because in observation 2, the identifiers are the same as 
> observation 3.
> >
> > Thanks for your help,
> >
> > Jeff Rosen
> 
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