---------- Forwarded message ----------
From: alexander russell <[email protected]>
Date: Tue, Oct 20, 2009 at 4:34 PM
Subject: Re: [R] When modeling with negbin from the aod package...
To: Matthieu Lesnoff <[email protected]>
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 <
[email protected]> 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]]
______________________________________________
[email protected] 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.
