Hi all, I'm trying out R's optimization functions (nlm() and optim()) in order to obtain parameter estimates for a combination of distributions. I've got my likelihood function, and optim() is happy to provide estimates (nlm() less so), but I'm concerned that uneven parameter scaling may be influencing the solutions. Does anyone know of any good references for application of nonlinear optimization that address this issue? Google returns vast quantities of information on NLM techniques, but I haven't found much on this topic. Thanks in advance, Dave -- Post-doctoral Fellow Neurology Department University of Iowa Hospitals and Clinics davideugenewarren@gmail.com [[alternative HTML version deleted]]