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

["Michael S. Hanson" <mshanson@mac.com>]

On Jun 16, 2006, at 2:01 PM, JEFFREY ROSEN wrote:

> 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
I haven't really been following this discussion, but:

	tsset hhold rd
	gen incomedifference = D.income

If you are *positive* you want zeros for "incomedifference" in round  
1, rather than the missing values that are automatically placed there  
by the above command and may be more appropriate for later analysis,  
then also:

	replace incomedifference = 0 if rd == 1

Hope this helps.

                                        -- Mike


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