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| From | Saki Tapsell <sakiuchiyama@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | Re: st: Mlogit with factor variables |
| Date | Wed, 23 Jan 2013 08:24:36 +0000 |
Thank you very much Maarten! On 22 January 2013 13:23, Maarten Buis <maartenlbuis@gmail.com> wrote: > On Tue, Jan 22, 2013 at 1:50 PM, Saki Tapsell wrote: >> I run the multinomial logit model with using y as dependent variable, >> and sector and firm_size as independent variables. >> >> "Sector" is a factor variable (1 = food, 2 = tobacco, 3 = textiles, 4 >> = apparel). >> >> I can do: >> >> mlogit y ib1.sector firm_size >> >> But the tobacco sector has a very small sample, so I don't want to >> include that but without dropping that data entirely. So I do: >> >> mlogit y i1.sector i3.sector i4.sector firm_size >> >> Which seems to work. mlogit uses sector == 1 as the base. > > That must be incorrect. With that syntax Stata must use sector==2 as > the base, which is not what you wanted > >> But now I want to use the command "prchange" which doesn't like factor >> variables. So I have to convert this to dummy variables. But if I >> do: >> >> mlogit y sector1 sector3 sector4 firm_size >> >> Then it no longer uses sector1 as the base. and I think treats them >> as binary independent variables. > > It is equivalent to your previous (wrong) syntax: the base is sector == 2. > > You have two options: either you drop all tobacco industries or you > merge the category tobacco with some other category, probably food. > > For the first option type: > > drop if sector == 2 > > or alternatively (better): > > gen byte touse = ( sector != 2 ) > mlogit y i.sector firm_size if touse == 1 > > I often abreviate this as: > mlogit y i.sector firm_size if touse > > For the second option type > gen sector2 = sector > replace sector2 = 1 if sector2 == 2 > mlogit y i.sector2 firm_size > > Hope this helps, > Maarten > > --------------------------------- > Maarten L. Buis > WZB > Reichpietschufer 50 > 10785 Berlin > Germany > > http://www.maartenbuis.nl > --------------------------------- > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/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/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/