Re: [ECOLOG-L] script for occupancy models in R

2010-12-20 Thread David Hewitt
Malcolm, Have a look at the package 'unmarked' for a direct implementation of some flavors of OMs in R. http://cran.r-project.org/web/packages/unmarked Also look at package 'RMark' for constructing OMs for fitting in program MARK (results returned to R as objects). RMark is available here: http:/

Re: [ECOLOG-L] AIC and Occam's Razor

2010-12-02 Thread David Hewitt
What answers have you found and why were they unsatisfactory? First, use AICc, not AIC. See Burnham and Anderson 2002 or Anderson 2008 (Primer). Second, I think most all literature is rather clear that models with deltaAICc < 2 are basically equivalent. So of course you should report support for

Re: [ECOLOG-L] mac/endnote

2010-11-26 Thread David Hewitt
Hilit, You don't have to be a whiz to use LaTeX, especially not now with LyX: www.lyx.org One of its greatest advantages for me is the reference handling (combined with JabRef). Give 'em a try, and save yourself a pile of $ in the process. - Dave Hewitt From: Hilit Finkler Subject: mac/end

Re: [ECOLOG-L] Zero CI

2010-07-28 Thread David Hewitt
Short answer: No. You probably don't have enough data to estimate what you want to estimate. Long answer: You didn't provide enough information for anyone to help you. Do some searching on the forum dedicated to such modeling in MARK at http://www.phidot.org/forum and then follow up with folks the

Re: [ECOLOG-L] Comparing slopes and intercepts in linear regressions

2010-04-07 Thread David Hewitt
Hi Andrew, My message was predicated on the poster (Howie) treating his analysis using ANCOVA in its simplest typical form, a single-factor covariance model. The "full" model is the one you give as #3. A start of an answer to your first question would be that the ANOVA table for this "full" model

Re: [ECOLOG-L] Comparing slopes and intercepts in linear regressions

2010-04-01 Thread David Hewitt
I certainly agree with Gareth that the ANCOVA approach should be simple. But it won't address all hypotheses posed by the "slopes and/or intercepts" framework. What you need is a model selection approach. Fit the various linear models of interest (some of which may be ANCOVA-type models), calculate

Re: [ECOLOG-L] AIC, data-dredging, and inappropriate stats

2010-02-09 Thread David Hewitt
> Date:    Mon, 8 Feb 2010 13:57:54 -0500 > From:    Bruce Robertson > Subject: AIC, data-dredging, and inappropriate stats > > Dear Ecologists, > > I've been using an information-theoretic model-selection approach as a > part of my research and have found that the ecological literature > appears

Re: [ECOLOG-L] ECOLOG-L Digest - 10 Jun 2009 to 11 Jun 2009 (#2009-162)

2009-06-12 Thread David Hewitt
Isabelle, I don't think any statistical method will do you much good if you only have four subjects. If you have a larger sample size such that some general inference about a treatment effect is reasonable, here's two references worth checking out: Gelman and Hill. 2007. Data analysis using regr

Re: [ECOLOG-L] Help: software

2009-06-09 Thread David Hewitt
anced data. R http://www.r-project.org/ See Documentation -> Manuals to get started on setting up the model(s), including the many excellent contributed documentation sources. ---------- David Hewitt Research Fishery Biologist USGS Western Fisheries Research Ce