Thanks, Professor Ripley. It helps a lot. As a follow-up question, is there any recommended references I can look into to figure out the interpretation of "weights" for various families?
Thanks very much in advance Best regards Ronggui On 24 April 2012 21:56, Prof Brian Ripley <rip...@stats.ox.ac.uk> wrote: > On 24/04/2012 14:36, Wincent wrote: >> >> Hi all, >> >> The nobs method of (MASS:::polr class) takes into account of weight, >> but nobs method of glm does not. I wonder what is the rationale of >> such design behind nobs.glm. Thanks in advance. Best Regards. >> >>> library(MASS) >>> house.plr<- polr(Sat ~ Infl + Type + Cont, weights = Freq, data = >>> housing) >>> house.logit<- glm(I(Sat=='High') ~ Infl + Type + Cont, binomial,weights = >>> Freq, data = housing) >>> nobs(house.plr) >> >> [1] 1681 >>> >>> nobs(house.logit) >> >> [1] 72 >> > > Well, the interpretation of 'weights' for a GLM depends on the family. They > may be equivalent to duplicated observations for a binomial GLM, but they > are not for a Gaussian one. The nobs method for class "glm" (there is no > visible nobs.glm) follows the "lm" method. > > -- > Brian D. Ripley, rip...@stats.ox.ac.uk > Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ > University of Oxford, Tel: +44 1865 272861 (self) > 1 South Parks Road, +44 1865 272866 (PA) > Oxford OX1 3TG, UK Fax: +44 1865 272595 -- Wincent Ronggui HUANG Sociology Department of Fudan University PhD of City University of Hong Kong http://homepage.fudan.edu.cn/rghuang/cv/ ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel