---------- Forwarded message ---------- From: alexander russell <ssv...@gmail.com> Date: Tue, Oct 20, 2009 at 4:34 PM Subject: Re: [R] When modeling with negbin from the aod package... To: Matthieu Lesnoff <matthieu.lesn...@gmail.com>
Hello again, It seems that, though we have a simple estimate of the variance, phi, with negbin, some models seek to create a formula for the variance. For example, I think Bolker has modeled variance in the Lily_sum data set as *nlikfun = function(a, c, d) {* *+ k = c * exp(d * flowers)* *+ -sum(dnbinom(seedlings, mu = a, size = k, log = TRUE))* *+ }* (book, p. 420) if I'm correct? Is it fair to say that the 'random' argument for negbin will model variance this way only if the independent variable on which the variance depends in the "right-hand formula" is categorical or is a factor with a few levels only? regards, s On Thu, Oct 15, 2009 at 5:53 PM, Matthieu Lesnoff < matthieu.lesn...@gmail.com> wrote: > >that is they are > > maximum likelihood estimates. Would someone tell me if I'm correct? > > yes, all parameters estimated with negbin (aod) are ML estimates > > Regards > > Matthieu > > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list 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.