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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 12:00:39 +0000 (GMT)
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 <[email protected]>
>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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>>-------- Оригинално писмо --------
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>>От: John Ataguba [email protected]
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>>Относно: st: Categorical variable in regression
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>>До: Statalist statalist mailing <[email protected]>
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>>Изпратено на: Сряда, 2013, Януари 23 13:22:09 EET
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>> Dear Statalist members
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>> I have a problem trying to let Stata display coefficients for all the categories of a categorical variable in a regression.
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>> Consider the example below:
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>> **********************************************
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>> clear
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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())
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>> gen y = 10+(56-10)*runiform()
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>> xi: reg y i.region, noconst noomit
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>> **********************************************
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>> 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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>> 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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>> I will appreciate your assistance.
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>> Regards
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>> Jon
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>> *
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>> * For searches and help try:
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>> * http://www.stata.com/help.cgi?search
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>> * http://www.stata.com/support/faqs/resources/statalist-faq/
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>> * 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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