[R] polr problem solved

Peter Flom flom at ndri.org
Sat Oct 9 04:11:09 CEST 2004

I'd like to thank John Fox and Chuck Cleland for their help in resovling
this issue.  It turned out to be something simple, but perhaps others
have had similar problems

In my original data frame, I had 4 categories of race/ethnicity.  One of
the categories (other) was very small, and not similar to any of the
other three categories, so I created a new data frame deleting those

However, the level "other" was still there, with no one in it.
This didn't cause a problem for glm or lm, but it did for polr.  When I
eliminated that level, the problem disappeared.

Thanks again for the help


Peter L. Flom, PhD
Assistant Director, Statistics and Data Analysis Core
Center for Drug Use and HIV Research
National Development and Research Institutes
71 W. 23rd St
New York, NY 10010
(212) 845-4485 (voice)
(917) 438-0894 (fax)

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