[R] convergence in polr
Prof Brian Ripley
ripley at stats.ox.ac.uk
Tue Feb 24 19:50:18 CET 2004
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?
> R-help at stat.math.ethz.ch mailing list
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Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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