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st: Re: xtrchh2/xtrchh

From   "Michael Blasnik" <>
To   <>
Subject   st: Re: xtrchh2/xtrchh
Date   Wed, 9 Jun 2004 11:28:31 -0400

If you can't run a simple OLS with the same variables on a given panel, then
xtrchh must drop the panel.  That's simply the nature of the estimator -- 
it's really a matrix-weighted average of the panel-specifc OLS estimates.  I
think the error message a fairly informative -- the panels are too small to
use the estimator, so they are dropped.

The "matrix has missing values" error I have also seen and I consider it a
small bug, the code should take care of that problem for you but it is
fairly easy to work around.

Michael Blasnik

----- Original Message ----- 
From: "Diego Rei" <>
To: <>
Sent: Wednesday, June 09, 2004 10:56 AM
Subject: st: xtrchh2/xtrchh

> Hello to all the Statalisters,
> I am trying to run the commands xtrchh/xtrchh2 on my models and I always
get the following message:
> "602 obs. dropped (panels too small)"
> Does anybody know why this is happening? Suspecting that it might depend
on the rather small number of cross sections relative to parameters to be
estimated, I eliminated some of the covariates and obtained :
> "matrix has missing values"
>  which is indeed true. I just would ask for a confirmation, is the xtrchh
command running with balanced panels only?Is the problem with panels too
small related to the number of panels with respect to the parameters or to
the time series dimension of the cross sections, or to something else?
> Thanks for any help.
> Have a good day

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