R help - Dec 2008 - Error fitting ZIP with zeroinfl()

I am attempting to fit a full zero-inflated Poisson model then use 
backward elimination to arrive at the best-fitting model.  When I try to 
fit the model with zeroinfl() I get this error:

Error in while (abs((ll_old - ll_new)/ll_old) > control$reltol) { :
        missing value where TRUE/FALSE needed

Any suggestions?

Thanks for your help!

Paige Barlow
MS Student
Virginia Tech
Dept Fish and Wildlife

On Thu, 11 Dec 2008, Paige Barlow wrote:
> I am attempting to fit a full zero-inflated Poisson model then use backward
> elimination to arrive at the best-fitting model.  When I try to fit the
model
> with zeroinfl() I get this error:
>
> Error in while (abs((ll_old - ll_new)/ll_old) > control$reltol) { :
>       missing value where TRUE/FALSE needed
>
> Any suggestions?
Read the posting guide linked at the end of the mail. The information 
above is really insufficient to say much useful.

The error message suggests that something in the specification of starting 
values is not correct. You seem to have used EM = TRUE, try (the default) 
EM = FALSE instead.
Z
> Thanks for your help!
>
> Paige Barlow
> MS Student
> Virginia Tech
> Dept Fish and Wildlife
>
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> PLEASE do read the posting guide
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>
>