About Passing Arguments to Function

 to add to what Haris said: I think you are trying to find the mle's of the
gamma, given some data,  and either what you're doing is not the right way
to do it  or maybe it's an alternative way to go about it that i am
unfamilar with. ?

i don't spend any  time maximizing likelihoods but roger peng has a very
nice example of how one can go about it using optim. i suggest that you take
a look at the attached document and then write out the likelihood for the
gamma similar to how i wrote it out for the poisson the other day in the
private email that i sent you.  in fact, the likelihood for the is probably
in any decent math stat book like casella and berger etc. if you have
johnson and kotz, it's definitely in there. if i had it here, i would just
tell you what it was.







On Thu, May 22, 2008 at  9:36 PM, Charilaos Skiadas wrote:

On May 22, 2008, at 9:14 PM, Edward Wijaya wrote:

Hi,

Below I have a function mlogl_k,
later it's called with "nlm" .

__BEGIN__
vsamples<- c(14.7, 18.8, 14, 15.9, 9.7, 12.8)

mlogl_k <- function( k_func, x_func, theta_func, samp) {
    tot_mll <- 0
    for (comp in 1:k_func) {
      curr_mll <- (- sum(dgamma(samp, shape = x_func,
scale=theta_func, log = TRUE)))
      tot_mll <- tot_mll + curr_mll
    }

    tot_mll
}

# Calling the function above
mlogl_out <- nlm(mlogl_k, mean(vsamples), k_func =2, x_func = 1,
theta_func = 1, samp=vsamples)

__END__

I thought under NLM, I already assign
the parameter correctly.
However it gives me the following error.

Error in f(x, ...) : unused argument(s) (14.3166666666667)
Calls: nlm -> <Anonymous> -> f
Execution halted


What's wrong with my code above?

nlm passes the following values over to mlogl_k: mean(vsamples), k_func
=2, x_func = 1, theta_func = 1, samp=vsamples

Now, f is called with these arguments, and all its arguments are matched
by the named arguments. Then it does not know what to do with the
"mean(vsamples)" argument. Hence the error: f is called with one more
argument than it can handle.

It is not clear with respect to what variables you want the minimization.
Right now all the named variables are treated as constants, and there is no
variable left with respect to which mlogl_k is supposed to be maximized.
Read the documentation for nlm carefully: Your function should have one more
argument (like the alpha in the question you asked yesterday).

- Edward

Haris Skiadas
Department of Mathematics and Computer Science
Hanover College