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

["Michael Blasnik" <michael.blasnik@verizon.net>]

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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