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Re: st: RE: Imputed Missing Values with Uvis


From   Richard Williams <Richard.A.Williams.5@nd.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: Imputed Missing Values with Uvis
Date   Thu, 24 Feb 2005 18:28:31 -0500

At 10:03 PM 2/24/2005 +0000, you wrote:
You seem surprised at this.

If you don't know -x1-, you cannot
predict -y- from -x1 x2 x3-; and
so on.

If you do know -y- you don't need
to impute it.
If I understand Quang correctly, then the latter is exactly the point. -uvis- should have just plugged in the observed value for y rather than even try to impute it; but instead, it plugged in a missing value since one or more of the Xs for that case was missing.

I tried -uvis- on a data set where y was not missing but some values of x were. The generated y had missing data whereas the original y did not.

I'm not that familiar with the programs but if nothing else one work around might be

replace uvis_y = max(original_y, uvis_y)

where uvis_y is the var generated by uvis. If I've done this correctly, then whenever -uvis- generated an unnecessary MD code for y, the original non-missing value for y will get plugged back in.

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