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From |
"Martin Weiss" <Martin.Weiss1@gmx.de> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: "mfx, predict at(...)" evaluated at CONDITIONAL means? |

Date |
Sun, 15 Mar 2009 21:09:10 +0100 |

<> Couple of things: You cannot use locals in the -mfx- if you define permanent vars in the -egen- statement. I played around with the -if- qualifier as well, but that restricts the sample of which the mean is taken to the cases where -mpg- equals thirty while you want to adjust for mpg equal to thirty... Eva`s solution is most elegant, and I think she wins our little contest - hands down. HTH Martin -------- Original-Nachricht -------- > Datum: Sun, 15 Mar 2009 20:57:43 +0100 > Von: Christoph Carl Basten <cc.basten@googlemail.com> > An: statalist@hsphsun2.harvard.edu > Betreff: Re: st: "mfx, predict at(...)" evaluated at CONDITIONAL means? > Hi Martin and Eva, > > thank you very much for both your proposals, both of which seem to be > working well. > > As for Eva's: I earlier considered to do the whole probit only with if > mpg==30, and rejected this because I wanted to use the information > on all units, but adding the if... only at the mfx stage seems to > circumvent this problem. > > But Martin's suggestion made me wonder why the following approach does > not also work (it doesn't, I just don't see why): > > . sysuse auto, clear > . egen condmean_price = mean(price) if mpg==30 > . egen condmean_weight = mean(weight) if mpg==30 > . qui probit foreign mpg weight price > . mfx, at(mpg=30 price=`condmean_price' weight=`condmean_weight') > > Stata then tells me: 'weight' found where number expected; (and I get > the same error when putting "loc" in front of the two egen commands). > In Martin's solution, no such problem seemed to exist. Could you tell me > what did the trick there? > > Many thanks and best regards, > Christoph > > > > > > Eva Poen wrote: > > Christoph, > > > > I haven't had a closer look, but I think there is a very simple > > solution for your problem: you can simply use an if condition with > > -mfx-. Here is an example using the auto data: > > > > **** > > sysuse auto > > probit foreign mpg rep78 weight > > > > * marginal effects at conditional means of mpg and weight if rep78==3: > > mfx compute if rep78==3 > > > > * check if the last column really contains conditional means: > > sum mpg weight if e(sample) & rep78==3 > > **** > > > > I quickly checked Martin's solution, and it comes to the same results. > > > > Hope this helps, > > Eva > > > > > > > > 2009/3/15 Christoph Carl Basten <cc.basten@googlemail.com>: > > > >> Hi, > >> > >> when estimating the marginal effects (using e.g. "mfx") after a Probit > >> regression, I'd like to set one value (age) to a representative value, > say > >> 50 years, and have all other variables at the /conditional/ mean for > those > >> aged 50. > >> > >> From what I understand, if I specify only "mfx, predict at(age=50), > Stata > >> will set all other variables to the /population/ means, so the only way > to > >> have them set at the means conditional on age=50 would be to compute > all > >> these conditional means by hand and then specifying them manually in > the > >> atlist. > >> > >> But is there any option to tell Stata that I want age=50 and e.th. else > at > >> the conditional means? > >> > >> Thanks for your consideration and best regards, > >> Christoph > >> > >> > >> > > > > * > > * For searches and help try: > > * http://www.stata.com/help.cgi?search > > * http://www.stata.com/support/statalist/faq > > * http://www.ats.ucla.edu/stat/stata/ > > > > > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ -- Martin Weiss Hackersteigle 3 72076 Tübingen 00497071/793535 00491784597218 Psssst! Schon vom neuen GMX MultiMessenger gehört? Der kann`s mit allen: http://www.gmx.net/de/go/multimessenger01 * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: "mfx, predict at(...)" evaluated at CONDITIONAL means?***From:*Christoph Carl Basten <cc.basten@googlemail.com>

**Re: st: "mfx, predict at(...)" evaluated at CONDITIONAL means?***From:*Eva Poen <eva.poen@gmail.com>

**Re: st: "mfx, predict at(...)" evaluated at CONDITIONAL means?***From:*Christoph Carl Basten <cc.basten@googlemail.com>

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