[R] polr and optim question

[John Fox]

Dear Peter,

It's hard to know from your message what the source of the problem might be,
but a good guess is that data are ill-conditioned in some way. Some things
to check: What's the distribution of the response variable? (Are there many
categories, some with very few observations?) How ill-conditioned is the
model matrix?

I hope this helps,
 John 
 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Peter Flom
> Sent: Friday, October 08, 2004 9:18 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] polr and optim question
> 
> 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)
> 
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