R-beta: anova.glm is broken with offsets
mikem at stat.cmu.edu
Wed Jun 3 16:14:04 CEST 1998
I have *not* tracked this bug very far because I hope someone who is more
familiar with the glm/anova code will jump in.
If one fits a glm model with an offset, the NULL deviance is incorrectly
calculated (it is calculated without the offset). The means one can get
examples where the model deviance is greater than the NULL deviance.
Here is some example output, (without the data).
> mymod <-glm(cens ~ group, family=poisson,offset=log(time))
Analysis of Deviance Table
Model: poisson, link: log
Terms added sequentially (first to last)
Df Deviance Resid. Df Resid. Dev
NULL 41 20.19
group 1 -17.83 40 38.02
Mike Meyer, Department of Statistics, Carnegie Mellon University
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch
More information about the R-help