[R] convergence in polr

[C. Spanou]

I am really sorry. I was supposed to send it to the Splus users but by 
mistake I sent to the R-users. Sorry once again



On Feb 24 2004, Prof Brian Ripley wrote:

> Why have you sent a message about S-PLUS to R-help, one that has already 
> been answered on S-news?
> 
> There is no function nlminb in R.
> 
> On 24 Feb 2004, C. Spanou wrote:
> 
> > Hello splus-users, I am trying to fit a regression model for an 
> > ordered response factor. So I am using the function polr in 
> > library(MASS). My data is a matrix of 1665 rows and 63 columns (one of 
> > the column is the dependent variable). The code I use is 
> > polr(as.ordered(q23p)~.,data=newdatap)
> >  but I am getting the following warning message singularity 
> > encountered in: nlminb.1(temp, p, liv, lv, objective, gradient, bounds, 
> > scale)
> > 
> > I looked in the MASS help for nlminb and I found that for the function
> > nlminb(start, objective, gradient=NULL, hessian=NULL,  
> >        scale=1, control=NULL, lower=-Inf, upper=Inf) 
> >  
> > 
> > when returning a warning message of singularity means that the 
> > optimization algorithm thinks it can't make any further progress 
> > because it has too many degrees of freedom. It usually means that the 
> > objective function is either not differentiable, or it may not have an 
> > optimum.
> > 
> > So for my data an optimum can't be obtained.
> > Is this true?
> > 
> > Can I ignore this warning message since what I want to find is values 
> > for the boundaries? Will the values for the boundaries be accurate even 
> > though I get the warning message?
> > 
> > ______________________________________________ 
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> > the posting guide! http://www.R-project.org/posting-guide.html
> > 
> > 
> 
>