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From |
Megan Sheahan <megan.sheahan@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: Other forums [was: RE: st: RE: how to force same excluded groups across regression models] |

Date |
Wed, 12 Oct 2011 12:16:06 -0700 |

Richard - I think you pointed me in the correct direction. Thanks! However, it seems to work for -regress-, but not when I regress using -xtreg-. Any thoughts on why that might be? There is no help in the manual. Fernando - Thanks for your suggestion. Stata still does strange things when I create separate dummies for each category and interact them separately. Megan On Wed, Oct 12, 2011 at 11:54 AM, Fernando Rios Avila <f.rios.a@gmail.com> wrote: > Hi Megan, > I know this is a more simple solution, but perhaps you should try to > create the dummies and interaction terms before the different > specifications are estimated, so you can have more control on which > variable is used as baseline reference. > regards, > Fernando > > On Wed, Oct 12, 2011 at 2:38 PM, Megan Sheahan <megan.sheahan@gmail.com> wrote: >> Thanks Nick. I'll try my question again on here. >> >> I am attempting to run the same model as pooled OLS, fixed effects, >> and CRE. There are a number of interaction terms in my model with >> categorical variables. When Stata runs these three models, it chooses >> different groups to exclude in the FE model than in the OLS and CRE >> models, making the output difficult to compare. For example, I am >> interacting three zone groups and four soil groups with N. The CRE and >> OLS models keep all three zones and omit the fourth soil group. The FE >> model omits the first zone and keeps all four soil groups. Is there >> any way to tell Stata to exclude the same groups across regression >> models? I tried the following command, but it did not fix the problem: >> char varname[omit]. >> >> For reference, here is the syntax for the three models: >> >> /* POOLED OLS */ regress yield_ha c.N_ha#zone_comb >> c.N_ha#c.N_ha#zone_comb c.N_ha#c.P_ha#zone_comb >> c.N_ha#soil_group_megan c.N_ha#c.rain_stress#zone_comb seed_ha >> c.seed_ha#c.seed_ha hectares c.hectares#c.hectares masset_ha >> c.masset_ha#c.masset_ha rain_stress i.manure i.hybrid >> c.rain_stress#hybrid i.legume i.crop_per_field i.dist i.FAO_class >> i.year if prod_func == 1, cluster(hhid) >> >> /* FE */ xtreg yield_ha c.N_ha#zone_comb c.N_ha#c.N_ha#zone_comb >> c.N_ha#c.P_ha#zone_comb c.N_ha#soil_group_megan >> c.N_ha#c.rain_stress#zone_comb seed_ha c.seed_ha#c.seed_ha hectares >> c.hectares#c.hectares masset_ha c.masset_ha#c.masset_ha rain_stress >> i.manure i.hybrid c.rain_stress#hybrid i.legume i.crop_per_field >> i.dist i.FAO_class i.year if prod_func == 1, fe i(hhid) cluster(hhid) >> >> /* CRE, WITH POOLED OLS STRUCTURE */ regress yield_ha c.N_ha#zone_comb >> c.N_ha#c.N_ha#zone_comb c.N_ha#c.P_ha#zone_comb >> c.N_ha#soil_group_megan c.N_ha#c.rain_stress#zone_comb seed_ha >> c.seed_ha#c.seed_ha hectares c.hectares#c.hectares masset_ha >> c.masset_ha#c.masset_ha rain_stress i.manure i.hybrid >> c.rain_stress#hybrid i.legume i.crop_per_field i.dist i.FAO_class >> i.year mN_ha mP_ha mseed_ha mhectares mrain_stress mmanure mhybrid >> mlegume mcrop_per_field if prod_func == 1, cluster(hhid) >> >> Many thanks in advance for your suggestions. >> >> Megan >> >> >> On Wed, Oct 12, 2011 at 11:22 AM, Nick Cox <n.j.cox@durham.ac.uk> wrote: >>> Stata tech support, if it falls within their remit? >>> >>> The main other forum I know of is Stack overflow. There is much less Stata traffic there than on this list. >>> >>> StataCorp is now on Facebook and Twitter but neither seems well suited to detailed technical questions or answers. >>> >>> Without bias, and without prejudice of any kind, I'd say that there are more, and more active, experts on this list... >>> >>> But what is it that can't be answered in this forum? >>> >>> Very broadly, and without reference to your thread, three main kinds of questions have low probabilities of getting detailed answers on this list. These are expressed in their limiting forms: >>> >>> * How should I analyse my data? >>> >>> * I am doing X. Is this correct? >>> >>> * I am new to Stata. Please give me a personal tutorial on A and B. >>> >>> And I don't think other lists are, in practice, more reactive to such questions. >>> >>> Nick >>> n.j.cox@durham.ac.uk >>> >>> Megan Sheahan >>> >>> Thanks again, Dave. For the broader audience, do you happen to know >>> where else I can submit a Stata question if it can't be answered >>> through this listserv? >>> >>> >>> * >>> * 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/ >> > > * > * 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/

**Follow-Ups**:**Re: Other forums [was: RE: st: RE: how to force same excluded groups across regression models]***From:*Richard Goldstein <richgold@ix.netcom.com>

**References**:**st: how to force same excluded groups across regression models***From:*Megan Sheahan <megan.sheahan@gmail.com>

**st: RE: how to force same excluded groups across regression models***From:*"Jacobs, David" <jacobs.184@sociology.osu.edu>

**Re: st: RE: how to force same excluded groups across regression models***From:*Megan Sheahan <megan.sheahan@gmail.com>

**RE: st: RE: how to force same excluded groups across regression models***From:*"Jacobs, David" <jacobs.184@sociology.osu.edu>

**Re: st: RE: how to force same excluded groups across regression models***From:*Megan Sheahan <megan.sheahan@gmail.com>

**Other forums [was: RE: st: RE: how to force same excluded groups across regression models]***From:*Nick Cox <n.j.cox@durham.ac.uk>

**Re: Other forums [was: RE: st: RE: how to force same excluded groups across regression models]***From:*Megan Sheahan <megan.sheahan@gmail.com>

**Re: Other forums [was: RE: st: RE: how to force same excluded groups across regression models]***From:*Fernando Rios Avila <f.rios.a@gmail.com>

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