st: Fw: AW: drop command & missing values

["Francesco Trivieri" <francesco.trivieri@unical.it>]

----- Original Message ----- 
From: "Francesco Trivieri" <francesco.trivieri@unical.it>
To: <statalist@hsphsun2.harvard.edu>
Sent: Monday, October 12, 2009 2:16 PM
Subject: Re: AW: drop command & missing values


> Dear Martin,
>
> thank you very much. I eventually understood the problem. It was depending 
> on the lagged dependent variable. If I do
>
> 1) drop if x>123
> rather than
> 2) drop if x>123 & x!=.
>
> I am eliminating observations that Stata may use to calculate Y-1. So, I 
> avoid the problem by using 2).
>
> Best regards
> Francesco
>
>
> ----- Original Message ----- 
> From: "Martin Weiss" <martin.weiss1@gmx.de>
> To: <statalist@hsphsun2.harvard.edu>
> Sent: Monday, October 12, 2009 1:47 PM
> Subject: st: AW: drop command & missing values
>
>
> > <>
> >
> > Well, in the absence of an example that is reproducible to all it is
> > difficult to diagnose the problem. In my example, both approaches end up
> > delivering the same nobs...
> >
> >
> > *************
> > use http://www.stata-press.com/data/r7/abdata.dta, clear
> >
> > replace w=. in 200/250
> >
> > preserve
> > drop if w>3.4
> > xtabond2 n w k, iv(w k, eq(level)) small h(1)
> > restore
> >
> > preserve
> > drop if w>3.4 & w!=.
> > xtabond2 n w k, iv(w k, eq(level)) small h(1)
> > restore
> > *************
> >
> >
> >
> > HTH
> > Martin
> >
> >
> > -----Ursprüngliche Nachricht-----
> > Von: owner-statalist@hsphsun2.harvard.edu
> > [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Francesco
> > Trivieri
> > Gesendet: Montag, 12. Oktober 2009 12:36
> > An: statalist@hsphsun2.harvard.edu
> > Betreff: st: drop command & missing values
> >
> > Dear Maarten and Martin,
> >
> > thank you very much for your answers. I am always including the x 
> > variable
> > in my estimation, I don't understand why:
> >
> > drop if x>123
> > xtabond2    Y   Y_1    X    Z ....
> > the estimation sample is 8100
> >
> > drop if x>123 & x!=.
> > xtabond2    Y   Y_1    X    Z ....
> > the estimation sample is 12200
> >
> > thanks again
> > Francesco
> >
> > *
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> >
> >
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