John
At 02:16 PM 1/20/2004 +0100, Roger Bivand wrote:
I contacted John Fox about this first, because parts of the file are attributed to him. He says that he didn't write rstandard.glm(), and suggests asking r-devel.
As it stands, rstandard.glm() has summary(model)$dispersion outside the sqrt(), while in rstandard.lm(), the sd is already sqrt()ed. This seems to follow stdres() in VR/MASS/R/stdres.R.
Of course for the c("poisson", "binomial") families, summary(model)$dispersion is 1, so sqrt doesn't make a difference, but working with an epidemiologist, Marilia Carvalho, we wanted to map the standardised residuals of a quasipoisson null model of cases offset by log(pop.at.risk), and rstandard.glm() seemed to compress the values more than we'd have expected. Her colleague: "Valeska (L. Andreozzi) says that she has already noticed that, and as McCullagh & Nelder (2nd ed, pg 397) says, the dispersion is inside the sqrt". (That's the way I read 12.5 on p. 397 too). I can't see that summary(model)$dispersion has already been subject to sqrt() in sum(object$weights * object$residuals^2)/df.r in summary.glm().
Should:
res / (summary(model)$dispersion * sqrt(1 - infl$hat))
be:
res / (sqrt(summary(model)$dispersion * (1 - infl$hat)))
on line 117 in base/R/lm.influence.R?
Best wishes,
Roger
-- Roger Bivand Econonic Geography Section, Department of Economics, Norwegian School of Economics and Business Administration, Breiviksveien 40, N-5045 Bergen, Norway, voice: +47-55959355, fax: +47-55959393; [EMAIL PROTECTED]
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----------------------------------------------------- John Fox Department of Sociology McMaster University Hamilton, Ontario, Canada L8S 4M4 email: [EMAIL PROTECTED] phone: 905-525-9140x23604 web: www.socsci.mcmaster.ca/jfox
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