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

 From JEFFREY ROSEN 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

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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```