R-beta: Re: glm
Peter Dalgaard BSA
p.dalgaard at biostat.ku.dk
Fri Jul 10 19:30:02 CEST 1998
Jim Lindsey <jlindsey at luc.ac.be> writes:
>
> Peter, I am currently in Britain on my way to read a paper before the
> RSS next week, but completely forgot to tell you before I left that
> you correction for the Inf in glm is not sufficient. You have to
> eliminate the last else and change the second if else to an else
> so that the Inf s are not set. Jim
?? (Perhaps what I said wasn't what I did?)
> summary(glm.D93)
Call:
glm(formula = counts ~ outcome * treatment, family = poisson)
Deviance Residuals:
[1] 0 0 0 0 0 0 0 0 0
Coefficients [contrasts: unordered=contr.treatment ordered=contr.poly ]:
Estimate Std. Error z value Pr(>|z|)
(Intercept) 2.89037 0.23570 12.263 <2e-16 ***
outcome2 -0.05716 0.33820 -0.169 0.866
outcome3 -0.18232 0.34960 -0.522 0.602
treatment2 0.10536 0.32489 0.324 0.746
treatment3 0.32850 0.30912 1.063 0.288
outcome2.treatment2 -0.63599 0.51417 -1.237 0.216
outcome3.treatment2 0.18232 0.47140 0.387 0.699
outcome2.treatment3 -0.59677 0.48093 -1.241 0.215
outcome3.treatment3 -0.55165 0.49553 -1.113 0.266
---
Signif. codes: 0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1
(Dispersion parameter for poisson family taken to be 1)
Null deviance: 1.0581e+01 on 8 degrees of freedom
Residual deviance: 1.7532e-15 on 0 degrees of freedom
AIC: 59.632
Number of Fisher Scoring iterations: 1
Now what's wrong with that? ('cept that you don't like the stars...)
There's another problem, namely that setting dispersion to Inf in the
0 DF case doesn't seem to be too good an idea:
> summary(glm.D93)
Call:
glm(formula = counts ~ outcome * treatment, family = gaussian)
Deviance Residuals:
[1] 0 0 0 0 0 0 0 0 0
Coefficients [contrasts: unordered=contr.treatment ordered=contr.poly ]:
Estimate Std. Error z value Pr(>|z|)
(Intercept) 18 Inf 0 1
outcome2 -1 Inf 0 1
outcome3 -3 Inf 0 1
treatment2 2 Inf 0 1
treatment3 7 Inf 0 1
outcome2.treatment2 -9 Inf 0 1
outcome3.treatment2 3 Inf 0 1
outcome2.treatment3 -11 Inf 0 1
outcome3.treatment3 -10 Inf 0 1
(I.e. same thing with gaussian family). I think I'd rather have 0/NA/NA
in the last three columns. *And* those should be |t| not |z|, i.e.
est.disp should be true, also when there are no degrees of freedom.
Will fix for next release. Obviously, this is not nearly as important
as the known-dispersion cases because the display is useless whatever
you do.
--
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
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
mailing list