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Re: st: Problem with setting the right reference category when  using mlogit
From 
 
Richard Williams <[email protected]> 
To 
 
[email protected],        "[email protected]" <[email protected]> 
Subject 
 
Re: st: Problem with setting the right reference category when  using mlogit 
Date 
 
Thu, 04 Oct 2012 17:44:18 -0500 
See the help for -mlogit-. Use the -baseoutcome- option. The default 
is to choose the most frequent outcome, so recoding won't accomplish 
what you want.
At 04:17 PM 10/4/2012, Amal Khanolkar wrote:
Hi,
I've been running some multinomial logistic regression models using mlogit.
My dependent variable has three categories as follows:
tab moth_wtgainbybmi
mother's weight gain by |
 pre-pregnancy BMI, IOM |
             guidelines |      Freq.     Percent        Cum.
------------------------+-----------------------------------
        Weight gain low |     51,716       22.37       22.37
Weight gain appropriate |     66,311       28.68       51.05
       Weight gain high |    113,164       48.95      100.00
------------------------+-----------------------------------
                  Total |    231,191      100.00
When I run an mlogit model as follows:
mlogit moth_wtgainbybmi i.race age i.education i.smoking height 
i.parity married, rrr, if plural==1
the model automatically sets 'weight gain high', the third category 
in the above variable as the base outcome. I however would like the 
second category, 'weight gain appropriate' to be the 'base outcome'. 
The three categories above are coded as 0, 1, 2.
Even if I recode the variable, such that weight gain appropriate==1, 
weight gain low==2 and weight gain high==3,
the latter, 'weight gain high' still gets set as the 'base outcome' 
in the mlogit model.
How do I change my reference category in the above model?
(and strangely enough, I do NOT have the same problem if I use 
another categorical variable as a dependent variable in the above model).
Thanks,
/Amal
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Richard Williams, Notre Dame Dept of Sociology
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