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From |
"Austin Nichols" <austinnichols@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: predictions |

Date |
Fri, 7 Sep 2007 08:09:29 -0400 |

Johannes Geyer <JGeyer@diw.de>: The most powerful way to compare predictions at different X values is to add "fake" observations to the end of your data, and -predict- y for those obs. You can add four obs with g byte real=1 set obs `=_N+4' and -replace- each variable in X as appropriate, or edit x* age* in `=_N-3'/`=_N' to type them in the Data Editor. If it is tedious to calculate all the X variables from age and other primitives, you can put all those calculations inside a little program to be run both on your real data and any fake data you may append later. Then predict yhat li yhat x* age* in `=_N-3'/`=_N' to see the predictions. You will want to drop the obs after you're done listing, graphing, whatever, so that you don't include as real data in a subsequent regression. You can drop in `=_N-3'/`=_N' but I find starting with making an indicator of real data safer and easier, in which case you can just drop if mi(real) drop real On 9/7/07, Johannes Geyer <JGeyer@diw.de> wrote: > Dear all, > > I would like to estimate a linear model with several interactions: > > reg y age age2 age3 age4 x1 x2 x3 x4 age*x1 age*x2 .... age4*x3 age4*x4 > > Then I would like to compare results for different x, i.e. I have four > groups (and a base category) and they may differ in their age-profile. So > far I used Excel to calculate different profiles but I it is very > cumbersomely... That is why I am looking for a more convenient > post-estimation command. (I think the spost package does something similar > for categorical variables.) The problem arises because I do not want to > compare at sample means. > > I would be happy if somebody had an idea which command could help, > > thank you > > regards > > Johannes > > > > > > > > ---------------------- > Johannes Geyer > Deutsches Institut für Wirtschaftsforschung (DIW Berlin) > German Institute for Economic Research > Graduate Center > DIW Berlin > Mohrenstraße 58 > 10117 Berlin > Tel: +49-30-89789-258 > > * > * 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**:**st: predictions***From:*Johannes Geyer <JGeyer@diw.de>

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