[R] accuracy of GLM dispersion parameters

From Ben Bolker: I would trust the gamma.dispersion() result more, although I agree that the difference is worrisome. The way to look at this further would be to profile the dispersion parameter. As I recall there isn't such a built in option in MASS (profile.glm only profiles the

Re: [R] accuracy of GLM dispersion parameters

Thanks. That reference does indeed seem to have a detailed explanation of this issue. I'll invest some thought in a careful reading to see if I can figure it out. Tim Handley Research Assistant Channel Islands National Park (Will be working from both CHIS and SAMO) CHIS Phone: 805-658-5759 (Tue,

[R] accuracy of GLM dispersion parameters

I'm confused as to the trustworthiness of the dispersion parameters reported by glm. Any help or advice would be greatly appreciated. Context: I'm interested in using a fitted GLM to make some predictions. Along with the predicted values, I'd also like to have estimates of variance for each of

Re: [R] understanding the output from gls

Kingsford, Thanks for the information. As you suggest, if I don't hear from anyone else about the degrees of freedom issue in a couple days, I'll try r-devel. Also, while I appreciate your explanation of the correlation matrix produced by summary.gls, I'm afriad I don't have the statistical

[R] understanding the output from gls

I'd like to compare two models which were fitted using gls, however I'm having trouble interpreting the results of gls. If any of you could offer me some advice, I'd greatly appreciate it. Short explanation of models: These two models have the same fixed-effects structure (two independent,

Re: [R] lme, lmer, gls, and spatial autocorrelation

Manuel, Thanks for the reference. I printed it out and read through it this morning. I think I'm going to take a gls approach. I've spent the last couple weeks reading about spatial autocorrelation, and found that the world of SAC is large, complex, and requires more time than I currently have.

[R] lme, lmer, gls, and spatial autocorrelation

Hello folks, I have some data where spatial autocorrelation seems to be a serious problem, and I'm unclear on how to deal with it in R. I've tried to do my homework - read through 'The R Book,' use the online help in R, search the internet, etc. - and I still have some unanswered questions. I'd

Re: [R] lme, lmer, gls, and spatial autocorrelation

Bert - I took a look at that page just now, and I'd classify my problem as spatial regression. Unfortunately, I don't think the spdep library fits my needs. Or at least, I can't figure out how to use it for this problem. The examples I have seen all use spdep with networks. They build a graph,