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

 From "Michael S. Hanson" To statalist@hsphsun2.harvard.edu Subject Re: st: RE: Quick Question on how to drop individual observations Date Fri, 16 Jun 2006 14:24:01 -0400

```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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