[R] 2 questions about mle() /optim() function in stats4

[Muhtar Osman]

Dear All,

There are two things about mle() that I wasn't so sure.

1) can mle() handle vector based parameter? say
    ll<-function(theta=rep(1,20)){..............}
   I tried such function, it worked for "optim" but not for "mle".

2) is there a general suggestion for the maximum number of parameters
allowed to use in mle() or optim()?

Thank you.
Regards,

MJO