Passing a function argument through R-function nlm

Question

I am probably being unreasonable asking for help debugging a program, but I have spent a day and a half on this pretty simple bit of code and have run out of ideas. I am trying to optimise a function called "log.pr.data" with respect to its first argument.

Because the function optimise requires you to set bounds on the argument I decided to use nlm which only requires a starting point. I have checked with simple exampels that nlm is indeed able to pass functions as arguments. My problem is that I am unable to pass a function as an argument in this particular case.

So here is the objective function (with two print diagnostics). I want to maximise it with respect to the argument lambda.s. (As a matter of interest, I am not maximising a likelihood here. I am trying to optimise an importance sampler.)

log.pr.data<-function(lambda.s,n1,n0,lambda.star,psi0,tobs,g=T.chan){
           print("Function log.pr.data")
           print(g)
          psi.s<-boundary(lambda.s,g,psi0,tobs,n1,n0)
         -my.dbinom(n0*lambda.s,n0,lambda.star,log=TRUE)
}

I have no problems with the command:

nlm(log.pr.data,p=0.6,n1=n1,n0=n0,lambda.star=lambda.star,psi0=psi0,tobs=tobs)

It works fine. But I want to be able to chance the function g=T.chan. So I redefined the function leaving g unspecified in log.pr.data. In other words, I just removed the "=T.chan" in the argument list. I checked that the function works OK. For instance with the command

 log.pr.data(l,n1,n0,lambda.star,psi0,tobs,T.chan)

for a range of values of "l" and it works fine and gives the same values as the previous function where g=T.chan is specified in the argument list. So the function T.chan is being passed properly it appears.

I then try to optimise

nlm(log.pr.data,p=0.6,n1=n1,n0=n0,lambda.star=lambda.star,psi0=psi0,tobs=tobs,g=T.chan)

and I get the error

Error in nlm(function(x) f(x, ...), p, hessian, typsize, fscale, msg, : invalid NA value in parameter

It is also interesting that there does not seem to be a single call to log.pr.data because "Function log.pr.data" is not printed. In earlier attempts to trouble shoot this problem, I realised that I was using the symbol "f" for the function being passed and that this might cause problems because nlm called its obejctive function "f". So I changed it to "g" throughout.