[R] Determining cause of error?

[rkevinburton at charter.net]

Now this is really specific. I think the cause of the error is a small sample size. For example. The following both fail:

fit <- fitdistr(c(120), "weibull")
fit <- fitdistr(jiitter(c(120,120), amount=0.5), "weibull")

As it is hard for me to control the sample size or the proximity of data values in the sample I was wondering how I can tell what the error modes for 'fitdistr' are? If I knew that 'fitdistr' will error out with a sample of of one or a sample of two values that are close then I could put a conditional statement an make a "reasonable" guess (something that I would expect 'fitdistr' to do). For example I could"

if(length(templist) > 1)
{
    fit <- fitdistr(templist, "weibull")
}

The problem is that I don't know all the possible error conditions. I know that having a sample size of 1 is bad and a sample of two "close" values is bad. Are there others?

Thank you.

Kevin

---- Henrik Bengtsson <hb at stat.berkeley.edu> wrote: 
> See ?traceback
> 
> /Henrik
> 
> On Wed, Aug 13, 2008 at 7:33 PM,  <rkevinburton at charter.net> wrote:
> > This is both a specific question and a general one. First, I am running 'fitdistr' from library(MASS) and I get the following:
> >
> > Error in fitdistr(templist, "weibull") : optimization failed
> >
> > What is the cause of the error? How can I tell? Can I just catch this error, report it and move to the next set of data (eat the exception)?
> >
> > Thank you.
> >
> > Kevin
> >
> > ______________________________________________
> > R-help at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >