Statalist


[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

Re: st: Problem with xtmixed


From   rgutierrez@stata.com (Roberto G. Gutierrez, StataCorp)
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Problem with xtmixed
Date   Wed, 04 Jun 2008 11:03:51 -0500

Noori Akhtar-Danesh <nakhtardanesh@cogeco.ca> is having difficulty getting
-xtmixed- to match -xtreg- and -gllamm-.  When running -xtmixed-, Noori
types the following:

   . xtmixed  birwt male ... pretri2 pretri3 || momid, mle

and the resulting estimation is having difficulty converging.  Noori has
simply omitted the colon after the group identifier -momid-, causing 
-xtmixed- to interpret the above as

   . xtmixed  birwt male ... pretri2 pretri3 || _all: momid, mle

an entirely different (and somewhat nonsensical in this case) model, hence
the failure to converge.  

Typing 

   . xtmixed  birwt male ... pretri2 pretri3 || momid:, mle

(with the colon after -momid-) will achieve the desired result.

Noori is not the first to be bit by this insidious bit of syntax.  The
original intent of providing a shortcut has proven in this case to not to be
worth the confusion it may cause.  As such, a future version of -xtmixed-
will require explicit specification of the level group identifier with the
colon, and issue a syntax error otherwise.

--Bobby
rgutierrez@stata.com
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index