st: RE: mlogit problem with "predict"

[Sheela Athreya <athreya@neo.tamu.edu>]

For those who have been helping me with the problem below, I thought  
an update would be useful: the problem was with the principal  
component scores themselves.  For some reason (I still have not  
figured out what) when I ran the PCA, several cases had scores of  
zero for every PC.

I reduced the number of variables in the pca, created new scores, and  
when I used fewer PC's (3 instead of 4) in my mlogit, the  
probabilities looked fine.

The use of -stripplot- helped--it seems PC3 and PC4 are almost  
identical in value.  I have no idea why.

Thanks again very much for all the help.

*******************************
Sheela Athreya, Ph.D.
Department of Anthropology
Texas A&M University
4352 TAMU
College Station, TX  77843
phone: 1-979-845-4785
fax: 1-979-845-4070



> > Hello,
> >
> > I am using Stata 9 for the PC, and have run the following command:
> >
> > mlogit tax pc1 pc2 pc3 pc4, vce(jackknife)
> >
> > Where (tax) has five outcomes
> >
> > The regression results seem to be fine, but when I then try to run  
> > "predict p1 p2 p3 p4 p5" to obtain posterior probabilities, I get  
> > the following:
> > "p1: 27 missing values generated"  (note: there are more than 27  
> > cases in the data set)
> >
> > And the resulting  posterior probabilities are completely off-- 
> > every value of p1 is either 0, 1 or missing  (".")
> > And, for a handful of cases, the values of p1-p5 are *all* 0.
> >
> > This also happens when I do not use the vce(jackknife) command,  
> > and when I use three instead of four independent variables.
> >
> > I suspect something is wrong among my cases (or variables) such  
> > that maybe two of my groups are so highly correlated that I am  
> > getting these results?  But I am not familiar enough with the  
> > principles of multinomial logit to know.  Any help or advice would  
> > be much appreciated.
> >
> > Many thanks,
> >
> >
> > *******************************
> > Sheela Athreya, Ph.D.
> > Texas A&M University
> > 4352 TAMU
> > College Station, TX  77843
> > phone: 1-979-845-4785
> > fax: 1-979-845-4070



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