> There is nothing in that plot to indicate that the result given by > optim() should be accepted as optimal. The numerical approximation to > the derivative is 0.055851 everywhere in your graph
That wasn't how I intended the plot to be interpreted. By default, the step size (in x) is 1e-5, which seems like a moderate step size. However, at that level, the numerical approximation is very badly behaved. And if the step size is decreased, things get worse. I haven't checked all the technical details of the optim function. But any reliance on numerical approximations of the derivative, have a high chance of running into problems using a function like this. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
