Re: st: Problem with setting the right reference category when using mlogit

[Richard Williams <richardwilliams.ndu@gmail.com>]

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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