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Re: st: RE: Quick Question on how to drop individual observations


From   "Michael Blasnik" <michael.blasnik@verizon.net>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: RE: Quick Question on how to drop individual observations
Date   Fri, 16 Jun 2006 14:26:07 -0400

How about:

bysort hhold (rd ): gen incdiff=income-income[_n-1]
by hhold (rd): replace incdiff=0 if _n==1

If you have time series data, you may want to look at ts commands that deal with any gaps more carefully. You should probably read up on using _n and _N with -by-

Michael

----- Original Message ----- From: "JEFFREY ROSEN" <rosen.53@osu.edu>
To: <statalist@hsphsun2.harvard.edu>
Sent: Friday, June 16, 2006 2:01 PM
Subject: Re: st: RE: Quick Question on how to drop individual observations



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


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