Hi Steve:

On Fri, Feb 5, 2010 at 10:10 AM, <Steve_Friedman@nps.gov> wrote:

>
> Hi everyone,
>
> I am trying to construct a glm and am running into a couple of questions.
>
> The data set I am using consists of 6 categories for the response and 6
> independent predictors representing nutrient concentrations at sample point
> locations.  Ultimately I'd like to use the probabilities for each response
> category in a simulation model such that these probabilities are used to
> define a realized ecological niche.
>

Isn't this a multinomial logistic regression model? I don't think this will
work
with glm(). I'd look into the rms package of Frank Harrell's group (function
lrm),
the VGAM package and the mlogit package for what I think are more
appropriate
alternatives. If the response is unordered, then multinomial() in the nnet
package is another alternative.

Laura Thompson has been maintaining a book-length project showing how to
use R/S-PLUS to do the exercises in Agresti's Categorical Data Analysis
book.
The latest version is here:

https://home.comcast.net/~lthompson221/Splusdiscrete2.pdf

Chapter 7 is on multinomial logit models (unordered and ordered).

HTH,
Dennis

	[[alternative HTML version deleted]]

