On Sat, 10 Nov 2007, Anders Schwartz Corr wrote:
> I'm getting an error message using polr():
>
> Error in optim(start, fmin, gmin, method = "BFGS", hessian =
Hess, ...) :
> initial value in 'vmmin' is not finite
>
> The outcome variable is ordinal and factored, and the independant variable
> is continuous. I've checked the source code for both polr() and optim()
> and can't find any variable called "vmmin" as referenced in
the error
> message.
vmmin is the C code for optim(method="BFGS"), so I don't know how
you
could have missed it. See line 304 of src/main/optim.c!
What you did not say is that you were using polr(method="cauchit"),
where
finding starting values is notoriously difficult. Either supply starting
values or call polr(..., Hess=TRUE) if you know you are going to be
calling summary() on the result.
>
> Any suggestions welcome.
>
> Thanks,
>
> Anders
>
>
>> summary(data$ordaodb)
> 0 1 2 3 4
> 8228 3505 1755 559 1757
>> summary(data$gpconc)
> Min. 1st Qu. Median Mean 3rd Qu. Max.
> 0.138 0.280 0.313 0.305 0.332 0.515
>> formula<-data$ordaodb~data$gpconc
>> propensityordaodb.plr <- polr(formula, method="cauchit")
>> propensityordaodb.plr
> Call:
> polr(formula = formula, method = "cauchit")
>
> Coefficients:
> data$gpconc
> 8.508
>
> Intercepts:
> 0|1 1|2 2|3 3|4
> 2.651 3.569 4.593 5.304
>
> Residual Deviance: 40009.85
> AIC: 40019.85
>> summary(propensityordaodb.plr)
>
> Re-fitting to get Hessian
>
> Error in optim(start, fmin, gmin, method = "BFGS", hessian =
Hess, ...) :
> initial value in 'vmmin' is not finite
--
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