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Re: st: Categorical variable in regression
From
John Ataguba <[email protected]>
To
"[email protected]" <[email protected]>
Subject
Re: st: Categorical variable in regression
Date
Wed, 23 Jan 2013 13:37:13 +0000 (GMT)
Dear Petya
Thanks very much for the second option :). I already know how to use the first option but wanted a quicker method.
Regards
Jon
>________________________________
> From: Petya Alexandrova <[email protected]>
>To: [email protected]
>Sent: Wednesday, 23 January 2013, 14:52
>Subject: Re: st: Categorical variable in regression
>
>I see. I am not sure if this works but you can try. Run the model
>without 'xi'. First create dummy variables out of your categorical
>variable.
>
>
>
>tabulate region, gen(reg)
>
>reg y reg*, noconst OR reg y reg1 reg2 reg3 reg4, noconst
>
>
>
>Btw, i saw the command with noomit somwehere written in the following
>way: xi, noomit: reg ... So, try typing your command like this:
>
>xi, noomit: reg y i.region, noconst
>
>
>
>I hope at least one of the options works!
>
>
>
>Petya
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>>-------- Оригинално писмо --------
>
>>От: John Ataguba [email protected]
>
>>Относно: Re: st: Categorical variable in regression
>
>>До: "[email protected]" <[email protected]>
>
>>Изпратено на: Сряда, 2013, Януари 23 14:00:39 EET
>
>
>
>
>> Thanks Petua for your response. Maybe my question was not clear enough. Note that I have suppressed the constant term in my regression - xi: reg y i.region, noconst noomit -. In that case there is no problem of the dummy trap. Based on Stata's documentation, the regression model I have specified is expected to run. Unfortunately, it is not running for me.
>
>>
>
>> I look forward to more response.
>
>>
>
>> Regards
>
>>
>
>> Jon
>
>>
>
>>
>
>> >________________________________
>
>> > From: Petya Alexandrova
>
>> >To: [email protected]
>
>> >Sent: Wednesday, 23 January 2013, 13:32
>
>> >Subject: Re: st: Categorical variable in regression
>
>> >
>
>> >In a regression with dummy variables one category is always omitted because it is the reference category.
>
>> >You can modify which category to be used as a reference group.
>
>> >
>
>> >Petya
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>> >
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>> >
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>> >
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>> >
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>> >
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>> >>-------- Оригинално писмо --------
>
>> >
>
>> >>От: John Ataguba [email protected]
>
>> >
>
>> >>Относно: st: Categorical variable in regression
>
>> >
>
>> >>До: Statalist statalist mailing
>
>> >
>
>> >>Изпратено на: Сряда, 2013, Януари 23 13:22:09 EET
>
>> >
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>> >
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>> >
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>> >
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>> >> Dear Statalist members
>
>> >
>
>> >> I have a problem trying to let Stata display coefficients for all the categories of a categorical variable in a regression.
>
>> >
>
>> >> Consider the example below:
>
>> >
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>> >>
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>> >
>
>> >> **********************************************
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>> >
>
>> >> clear
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>> >
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>> >> set obs 200
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>> >
>
>> >> set seed 12345
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>> >
>
>> >> gen region = 1+int((4-1+1)*runiform())
>
>> >
>
>> >> gen y = 10+(56-10)*runiform()
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>> >
>
>> >> xi: reg y i.region, noconst noomit
>
>> >
>
>> >> **********************************************
>
>> >
>
>> >>
>
>> >
>
>> >> I expect Stata to display the coefficients for all the four categories of the categorical variable named "region". However, Stata still omits one category. Is there something I am doing wrong?
>
>> >
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>> >>
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>> >
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>> >> I am running Stata 12.1 (SE) on Windows 7 platform. I also tried this in Stata 11.2 (IC) on Windows 7 platform and I obtained the same result.
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>> >
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>> >>
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>> >
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>> >> I will appreciate your assistance.
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>> >
>
>> >>
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>> >
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>> >> Regards
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>> >
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>> >>
>
>> >
>
>> >> Jon
>
>> >
>
>> >>
>
>> >
>
>> >> *
>
>> >
>
>> >> * 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:
>
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>
>> >* http://www.stata.com/support/faqs/resources/statalist-faq/
>
>> >* http://www.ats.ucla.edu/stat/stata/
>
>> >
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>> >
>
>> >
>
>>
>
>> *
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>> * For searches and help try:
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>*
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*
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