On Thu, 4 Dec 2003, Paul E. Johnson wrote: > I looked for examples of count data that might interest the students and > found this project about dropout rates in Los Angeles High Schools. It > is discussed in the UCLA stats help pages for the Stata users: > http://www.ats.ucla.edu/stat/stata/library/count.htm > and > See: http://www.ats.ucla.edu/stat/stata/library/longutil.htm > > To replicate those results, I used R's excellent foreign package to > bring the lahigh data in, then did > poisReg1 <- glm(daysabs~gender+ > mathnce+langnce,family=poisson(link=log), data=lahigh) > library(MASS) > negbinReg1 <- glm.nb(daysabs~gender+ mathnce+langnce,link=log, data=lahigh) > > The parameter estimates of the coefficients are the just about the same, > except for the intercept estimates. Below I pasted in the Negative > Binomial results I got from R along with the Stata results that they
Actually, from V&R's MASS package, excellent or otherwise but worthy of credit! > report. In the Stata output, they report alpha, same as 1/theta from > the R glm.nb output. Except for minor differences in standard errors, > only the intercept estimates markedly differ. What are the variable codings used? Intercepts depend on coding of factors, and that applies to any sort of regression. -- Brian D. Ripley, [EMAIL PROTECTED] 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 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help