[R] polr and optim question

[Peter Flom]

Hello again

I am trying to fit an ordinal logistic model using the polr function
from MASS.  When I run

model.loan.ordinal <- polr(loancat~age + sex + racgp + yrseduc +
 needlchg + gallery  + sniffball + smokeball + sniffher +
 smokeher + nicocaine + inject + poly(year.of.int,3)  + druginj +
inj.years)


I get an error 

Error in optim(start, fmin, gmin, method = "BFGS", hessian = Hess, ...)
: 
        non-finite value supplied by optim


I checked in the MASS book, and in John Fox's book An R and S-Plus
Companion to Applied Regression,  I also checked in R-help, where a
similar problem was solved by using as.ordered, but that did not help
here.

Any help appreciated

Thanks



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
www.peterflom.com
New York, NY 10010
(212) 845-4485 (voice)
(917) 438-0894 (fax)