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Re: st: mim: xtmixed for unconditional models


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: mim: xtmixed for unconditional models
Date   Thu, 23 Apr 2009 07:46:17 +0000 (GMT)

Apperently your model is not identified in your third imputed 
dataset. That can happen in complex models like -xtmixed-.
You can check that by typing:

xtmixed dvar if _mj==3 || schid: || childid:

You can "solve" this by either creating a new set of imputed 
datasets and hope that the model is identified in all new 
datasets, or just drop the third dataset (-drop if _mj==3-).

-- Maarten

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

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


--- On Wed, 22/4/09, Nailing Xia <nailingxia@gmail.com> wrote:

> From: Nailing Xia <nailingxia@gmail.com>
> Subject: st: mim: xtmixed for unconditional models
> To: statalist@hsphsun2.harvard.edu
> Date: Wednesday, 22 April, 2009, 9:55 PM
> Hi,
> 
> I am estimating multilevel models with mulple imputed data
> (using
> -ice-). I have got results from the full model using
> command - "mim:
> xtmixed dvar var1 var2 var3 if [wgt] || schid: ||
> childid:". However,
> I have problems getting results when estimating the
> unconditional
> model (i.e., no independent variables, only intercept). I
> have tried
> two commands - "mim: dvar if [wgt] || schid: ||
> childid:"  and "mim:
> dvar one if [wgt] || schid: || childid:" (the variable
> one equals to 1
> for all observations). Stata has run for days without
> giving any
> estimates (whereas it took 7 hours for Stata to estimate
> the full
> model) - it seems to be stuck at estimaing for m=3. I have
> tried both
> commands without using -mim-, and both worked fine and gave
> the same
> results. Does anyone know why the unconditional model take
> so long
> when using -mim-? Is there a faster way to do it?
> 
> Thank you.
> 
> Nailing Xia
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