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From |
Quang Nguyen <quangn@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: Imputed Missing Values with Uvis |

Date |
Thu, 24 Feb 2005 14:10:52 -1000 |

Dear Nick and Richard, Thanks so much for your advices. I highly appreciate it. Yes I do understand that we need to impute "y" ONLY for observations with missing values. Uvis, however, imputes "y" for all observations. As a result, the imputed "y" might has missing value if any of "x" is missing on a given observation. Thanks Richard for offering an execellent way of dealing with this interesting issue. I truly enjoy this forum where any of my question is answered just moments after it posted. You are GREAT! Have A Wonderful Day! All the best, Quang On Thu, 24 Feb 2005 23:36:07 -0000, Nick Cox <n.j.cox@durham.ac.uk> wrote: > No doubt this is what is often > wanted. But the help for -uvis- > is explicit: > > Note that uvis will not impute observations for which > a value of a variable in xvarlist is > missing. Only complete cases within xvarlist are used. > > Nick > n.j.cox@durham.ac.uk > > Richard Williams > > > 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. > > * > * 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/ > * * 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/

**References**:**RE: st: RE: Imputed Missing Values with Uvis***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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