Dear R-users:
How does one calculate in R  the odds ratios for a CATEGORICAL predictor 
variable that has 4 levels.  I see r-help inquiries regarding odds ratios 
for what looked like a continuous predictor variable.  I was wondering how 
to get the pairwise odds ratios for comparisons of levels of a categorical 
predictor variable.  I can't seem to get the correct output using:
 > sp.glm=glm(cohort$logreg~cohort$hab, family=binomial)
 > summary(sp.glm)

This gives me the coefficient for the effect of hab overall, but not the 
coefficients for the comparisons of each of the levels. I suspect this has 
something to do with the contrasts statement, but I can't figure it out, 
and would be very appreciative of any help you can provide.
Thank you,
Sabrina

______________________________________________________________
Sabrina E. Russo
Postdoctoral Fellow
Center for Tropical Forest Science - Arnold Arboretum Asia Program
Harvard University
22 Divinity Avenue
Cambridge, MA 02138 USA

617-496-2380 phone
617-495-9484 FAX
srusso@oeb.harvard.edu



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