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st: mlogit problem with "predict"


From   Sheela Athreya <athreya@neo.tamu.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: mlogit problem with "predict"
Date   Mon, 06 Aug 2007 11:41:20 -0500

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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