Edward, you also can use the package aod on CRAN, see the help page of the
function negbin.
Best
Matthieu
An example:
> library(aod)
> data(dja)
> negbin(y ~ group + offset(log(trisk)), ~group, dja, fixpar = list(4, 0))
Negative-binomial model
-----------------------
negbin(formula = y ~ group + offset(log(trisk)), random = ~group,
data = dja, fixpar = list(4, 0))
Convergence was obtained after 113 iterations.
Fixed-effect coefficients:
Estimate Std. Error z value Pr(> |z|)
(Intercept) -0.5526 0.2277 -2.4267 0.0152
groupTREAT -1.0205 0.2598 -3.9287 < 1e-4
Overdispersion coefficients:
Estimate Std. Error z value Pr(> z)
phi.groupCTRL 0.8287 0.412 2.0117 0.0221
Overdispersion coefficients set to fixed values:
Value
phi.groupTREAT 0
Log-likelihood = -121.149; nbpar = 3; df.residual = 72; Deviance = 111.826; AIC
= 248.297
________________________________
De: [EMAIL PROTECTED] de la part de Edward McNeil
Date: jeu. 6/30/2005 8:50
À: [EMAIL PROTECTED]
Objet : [R] Dispersion parameter in Neg Bin GLM
Hi,
Can someone tell me if it is possible to set the dispersion parameter constant
when fitting a negative binomial glm in R? I've looked at the documentation and
can't find the appropriate argument to pass.
In STATA I can type: nbreg depvar [indepvar...], offset(offset)
dispersion(constant).
Thank you
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