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RE: st: Data management


From   Nick Cox <n.j.cox@durham.ac.uk>
To   "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Data management
Date   Thu, 21 Oct 2010 11:52:19 +0100

Chris's approach is good, with the addition that the SD can be missing as well as zero; such observations are presumably of no interest either. 

He is also correct that there are other ways to do it, which follow from the principles explained in 

FAQ     . . . . . .  Listing observations in a group that differ on a variable
        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
        11/01   How do I list observations in a group that differ
                on a variable?
                http://www.stata.com/support/faqs/data/diff.html

So, for example, consider  

bysort hhn (rentaltype) : keep if rentaltype[1] != rentaltype[_N] 

Nick 
n.j.cox@durham.ac.uk 

Chris Parker

One option (I'm sure more concise options will follow) is:

bysort hhn: egen hasboth=sd(rentaltype)
drop if hasboth==0

This removes any observations where there is no variation in the
rental type across the household.

Jeetendra Aryal 

> I have a big data set which is as follows:
> HHN   PN    Rental type
> 1          1        1
> 1          2        0
> 1          3        0
> 2          1        1
> 2          2        1
> 3          1        1
> 3          2        0
> 3          3        1
> 4          1        1
> 4          2        1
> 4          3        1
> 5          1        0
> 5          2        1
> 5          3        1
>
> Now the question is: Each household has more than one plot of land. The household can use it or rent it out or both. I want to keep only those households which have both rental types. For example, in the above dataset I want to keep only household number 1, 3 and 5. Is there any way that I can do it easily, rather than doing manually?

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