On Fri, 2009-03-20 at 12:39 +1100, Gad Abraham wrote: > Maggie Wang wrote: > > Hi, Dieter, Gad, and all, > > > > Thank you very much for your reply! > > > > So here is my data, you can copy it into a file names "sample.txt" > > Hi Maggie, > > With this data (allowing for more iterations) I get: > > > lr <- glm(fo, family=binomial(link=logit), data=matrix, > control=glm.control(maxit=100)) > Warning message: > In glm.fit(x = X, y = Y, weights = weights, start = start, etastart = > etastart, : > fitted probabilities numerically 0 or 1 occurred > > which indicates, as Thomas has said, perfect separation, which occurs > because you're trying to fit too many variables with not enough data.
It is worth mentioning that, in and of itself, that warning does not necessarily indicate a separation issue - something I was unsure about recently. You can get that warning (and I did for several data sets in a recent problem I enquired on the list about) where the fitted values really do become numerically 0 or 1 without separation. For example, see this response to my original question on the list: http://article.gmane.org/gmane.comp.lang.r.general/134472/ There Ioannis Kosmidis presents a number of ways to investigate the results of a logit model fit for such issues. G > > Cheers, > Gad > -- %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% Dr. Gavin Simpson [t] +44 (0)20 7679 0522 ECRC, UCL Geography, [f] +44 (0)20 7679 0565 Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ UK. WC1E 6BT. [w] http://www.freshwaters.org.uk %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
signature.asc
Description: This is a digitally signed message part
______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
