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AW: st: Problem with xi (Stata 11)


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   AW: st: Problem with xi (Stata 11)
Date   Wed, 2 Jun 2010 15:45:13 +0200

<> 


This sounds like a problem that you should take up with Stata tech support,
as nobody else has been able to reproduce it.



HTH
Martin


-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Walter
Garcia-Fontes
Gesendet: Mittwoch, 2. Juni 2010 15:35
An: statalist@hsphsun2.harvard.edu
Betreff: Re: st: Problem with xi (Stata 11)

It seems a problem that I'm only able to reproduce in my machine, from
a fresh started stata and entering the following commands:

webuse set http://puna.upf.edu
webuse data/data
xi i.COUNTRY
ta COUNTRY  _ICOUNTRY_56, nol

   Country |
      code |      COUNTRY==56
   3-digit |         0          1 |     Total
-----------+----------------------+----------
        40 |     4,927          0 |     4,927 
        56 |       265      8,592 |     8,857 
       203 |     5,932          0 |     5,932 
       208 |     4,532          0 |     4,532 
       233 |     4,865          0 |     4,865 
       246 |     4,714          0 |     4,714 
       250 |     4,716          0 |     4,716 
       276 |     4,891          0 |     4,891 
       300 |     4,873          0 |     4,873 
       348 |     4,490          0 |     4,490 
       372 |     4,444        141 |     4,585 
       380 |    21,773          0 |    21,773 
-----------+----------------------+----------
     Total |    70,422      8,733 |    79,155 

I get this both in updated Stata 10 and Stata 11. 

My machine is a Dell Precision 690 running Ubuntu Gnu-Linux 10.04. 

I tried it also at a Sun server running Solaris and I can't reproduce
under Stata 10 (no Stata 11 there yet). 

So it seems some combination of a particular machine precision and the
xi command. 

tab COUNTRY, gen(_ICOUNTRY) 

works perfectly on the other hand. 

Walter


* Martin Weiss [02/06/10 15:10]:
> 
> <> 
> 
> 
> " Stata 11 users are encouraged officially to use factor variables"
> 
> 
> Walter may have a point, though, if all he wants is to use -xi- as a
> standalone command, to generate dummies for a categorical variable. -tab,
> gen()- may be an alternative.
> 
> 
> 
> HTH
> Martin
> 
> 
> -----Ursprüngliche Nachricht-----
> Von: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Roger Newson
> Gesendet: Mittwoch, 2. Juni 2010 15:01
> An: statalist@hsphsun2.harvard.edu
> Betreff: Re: st: Problem with xi (Stata 11)
> 
> I don't know what exactly is going on in your case. However, I do know 
> that Stata 11 users are encouraged officially to use factor variables 
> instead of -xi-, although -xi- should still work (and has done so for me 
> so far).
> 
> Best wishes
> 
> Roger
> 
> 
> Roger B Newson BSc MSc DPhil
> Lecturer in Medical Statistics
> Respiratory Epidemiology and Public Health Group
> National Heart and Lung Institute
> Imperial College London
> Royal Brompton Campus
> Room 33, Emmanuel Kaye Building
> 1B Manresa Road
> London SW3 6LR
> UNITED KINGDOM
> Tel: +44 (0)20 7352 8121 ext 3381
> Fax: +44 (0)20 7351 8322
> Email: r.newson@imperial.ac.uk
> Web page: http://www.imperial.ac.uk/nhli/r.newson/
> Departmental Web page:
>
http://www1.imperial.ac.uk/medicine/about/divisions/nhli/respiration/popgene
> tics/reph/
> 
> Opinions expressed are those of the author, not of the institution.
> 
> On 02/06/2010 13:47, Walter Garcia-Fontes wrote:
> > I have a problem with the "xi" command in Stata 11 (completely updated
> > as of today). I tried to create a dataset as simple as possible to
> > reproduce the problem, which can be accessed from my server. In the
> > dataset there is a single variable called COUNTRY with numeric codes
> > for each country and labels identifying the country.
> >
> > There are 12 different values for COUNTRY (12 different countries) and
> > 79155 observations with a variable number of observations for each
> country.
> > To reproduce:
> >
> > webuse set http://puna.upf.edu
> > webuse data/data.dta
> > xi i.COUNTRY
> >
> > Stata creates variables _ICOUNTRY_n as it should, where n are the
> > different codes for the 12 countries, omitting the country with the
> > smallest code.
> >
> > The problem is that some of the values of _ICOUNTRY are 0 when they
> > shouldn't be, for instance I have cases where _ICOUNTRY_56 = 0 but
> > COUNTRY = 56. This happens randomly for a few cases and I've looked at
> > it from all angles but couldn't figure out what is going on.
> >
> > If I reduce the number of variables or the number of observations the
> > problem  disappears at some point, can't tell exactly when, so I'm
> > providing the smallest example I could build.
> >
> > Walter
> >
> *
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> *   http://www.ats.ucla.edu/stat/stata/
> 
> 
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/

-- 
Walter Garcia-Fontes
mailto: walter.garcia@upf.edu - http://puna.upf.edu
Departament d'Economia i Empresa - http://www.econ.upf.edu
Universitat Pompeu Fabra
Ramon Trias Fargas 25-27, 08005 Barcelona, Spain
Tel. +34 93 542 2722 - Fax. +34 93 542 1746

*
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