[R] polr (MASS)

[John Fox]

Dear Naiara,

I believe that the problem is in your specification of start values: If the
two independent variables are numeric, then there are four parameters in the
model, not two--i.e., two regression coefficients and two thresholds (or
intercepts). But why do you find it necessary to specify the start values in
any event?

I hope this helps,
 John

--------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox 
-------------------------------- 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Naiara S. Pinto
> Sent: Tuesday, January 24, 2006 4:29 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] polr (MASS)
> 
> Hello all,
> 
> I am trying to use polr (the ordered logistic model from 
> MASS) but I am getting the following error message:
> 
> Error in if (all(pr > 0)) -sum(wt * log(pr)) else Inf :
> missing value where TRUE/FALSE needed
> 
> My response variable is a factor with 3 levels and I have 2 
> independent variables. I am not sure if I guessed the 
> starting parameters right, which I imagine could be a source 
> of error. Here's my code:
> 
> > polr(a~b+c, method="logistic", start=c(10, 0.06))
> 
> Does anyone have any ideas why I am getting this error message?
> 
> Thank you very much,
> 
> Naiara.
> 
> --------------------------------------------
> Naiara S. Pinto
> Ecology, Evolution and Behavior
> 1 University Station A6700
> Austin, TX, 78712
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html