using optimize() correctly ...

Hello Berend,

Berend Hasselman wrote:

Your function is not unimodal.
The help for optimize states: "If f is not unimodal, then  
optimize() may approximate a local, but perhaps
non-global, minimum to the same accuracy."

Ah ok, I didn't read the manual page carefully enough.

Do you know if R has a function to find the global maximum/minimum  
of a
function of x over a given interval?

If you do

  resopt <- optim(-5,f, method="SANN",control=list(fnscale=-1))

you will get the global maximum. SANN: simulated annealing. But  
starting in -4 takes you to the local maximum.

But the help for optim recommends optimize for one-dimensional  
maximization.

As far as I know there is no general foolproof method for finding a  
global optimum except trying different initial points.
No method can really replace one's own knowledge about a function.

Berend

btw. i am away during this week so i won't be replying.