On Dec 27, 2011, at 15:47 , Scott Raynaud wrote: > I have the following code (which I did not write) that generates > data based on a logistic model. I'm only getting a single record > with y=1. It seems implausible that in 50k cases that have a > single y=1. Does that ring alarm bells for anyone else? >
Not really. As far as I can tell, "fixpart" is roughly -10.5 (= -1.5 - .25*36), so binomprob is around 2.75e-5, which - nonlinearity notwithstanding - suggests that the expected number of positives out of 50K is something like 1.4. To do this more precisely, just compute and print sum(binomprob) in the code you gave. > beta<-c(-1.585600,-0.246900) > betasize<-length(beta) > meanpred<-c(0,35.900000) > varpred<-c(0,1.000000) > #loop code > x<-matrix(1,length,betasize) #length set to 50k > #loop code > x[,2]<-rnorm(length,meanpred[2],sqrt(varpred[2])) #length set to 50k > fixpart<-x%*%beta > binomprob<-exp(fixpart)/(1+exp(fixpart)) > data$y<-rbinom(n1,1,binomprob) > #more loop code > > ______________________________________________ > 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. -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd....@cbs.dk Priv: pda...@gmail.com ______________________________________________ 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.
