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


From   Richard Goldstein <richgold@ix.netcom.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 14:46:50 -0400

if I correctly understand your issue, you want to see -h fvvarlist- and
look in the "base levels" section

Rich

On 10/12/11 2:38 PM, Megan Sheahan 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/


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