Re: st: incorrect results seen when creating new variable by multiplying existing variables

[Maarten buis <maartenbuis@yahoo.co.uk>]

--- On Wed, 9/3/11, Mariano Matias Iberico wrote:
> I have a problem when trying to generate a new master variable to 
> identify clusters for an -expand– I use later. When passing into 
> 1000s of observations the newid variable becomes funky.

This is a precision problem. There are many sources where you can
read more about it. One that focusses on your type of problem, i.e.
generating a identifier variable is:
<http://www.ats.ucla.edu/stat/Stata/faq/longid.htm>

To take your example, you can fix it as follows:

*-------------- begin example ------------------
 sysuse nlsw88.dta, clear
 keep idcode age grade
 replace grade=1 if grade==.
 generate double newid=.       // <-- only this line was changed
 format %11.0g newid
 replace newid=_n*10000+age*100+grade
 list newid idcode age grade in 2236
*--------------- end example -------------------

Hope this helps,
Maarten

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://www.maartenbuis.nl
--------------------------


      

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