[R] Trouble with optim function

[Ian Fiske]

You're minimizing the log likelihood, but you want to minimize the *negative*
log likelihood.  Also, optimize() is better than optim() if you have a
function of only one argument.

Replace


Jon Moroney wrote:
> 
> #Create the log likelihood function
> LL<-function(x) {(trials*log(x))-(x*sumvect)}
> 
> optim(1,LL,method="BFGS")
> 

with

LL<-function(x) {-trials*log(x)+x*sumvect}
optimize(LL,c(0,1e5))

or better yet, to avoid errors and make generalizeable, do this

LL<-function(x) {-sum(dexp(vector,x,log=TRUE))}
optimize(LL,c(0,1e5)) 

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