peter dalgaard <pdalgd <at> gmail.com> writes:
>
>
> On Apr 19, 2012, at 09:52 , Joachim Audenaert wrote:
>
> > Hi all,
> >
> > I have some problems with the mle2 function
> >
> >
> >> RogersIIbinom <- function(N0,attackR3_B,Th3_B)
> {N0-lambertW(attackR3_B*Th3_B*N0*exp(-attackR3_B*(24-Th3_B*N0)))/
> (attackR3_B*Th3_B)}
> >> RogersII_B <-
> > mle2(FR~dbinom(size=N0,prob=RogersIIbinom(N0,attackR3_B,Th3_B)/N0),
> start=list(attackR3_B=1.5,Th3_B=0.04),method="Nelder-Mead",data=dat)
> > Error in dbinom(x, size, prob, log) :
> > Non-numeric argument to mathematical function
> >
> > Can somenone explain met what this error means? All my parameters and data
> > are defined, so I don't understand what the non-numeric argument is???
> > With different equations the script does work...........
>
> traceback() indicates that the prob= argument is a vector of
> complex numbers when doing the call
>
> minuslogl(attackR3_B = -0.262499999999999, Th3_B = 1.755625)
>
[snip]
Further debugging shows that this is caused by an attempt
to evaluate a negative attack-rate parameter.
The short answer is that if you use method="L-BFGS-B",
lower=1e-5 (you need to set the lower bound slightly *above* zero)
you can get this to work fine.
I have posted a longer, somewhat obsessive answer at
http://www.math.mcmaster.ca/bolker/misc/rogers2.pdf
which is an ongoing brain dump/set of notes about fitting
the Rogers random predator equation and related models in R.
Ben Bolker
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