[R] Error: function cannot be evaluated at initial parameters

[Rolf Turner]

On 19/09/2008, at 2:33 PM, sandsky wrote:

>
> I have an error for a simple optimization problem.

	It is not a simple optimization problem.  It is a
	totally silly optimization problem.

> Is there anyone knowing
> about this error?
>
> lambda1=-9
> lambda2=-6
> L<-function(a){
> s2i2f<-(exp(-lambda1*(250^a)-lambda2*(275^a-250^a))
>        -exp(-lambda1*(250^a)-lambda2*(300^a-250^a)))
> logl<-log(s2i2f)
> return(-logl)}
> optim(1,L)
>
> Error in optim(1, L) : function cannot be evaluated at initial  
> parameters

What is your difficulty?  The error means what it says.  Nothing  
more, nothing less.

Did you ***try*** just typing ``L(1)'' to see what you get?

Hint:  exp(2250) is infinity as far as your --- or anyone else's ---  
computer
is concerned.

	cheers,

		Rolf Turner

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