Get help. You do not understand glm's. What do you think the fitted values are? -- Hint: they are *not* an estimate of the number of living fruit flies.
-- Bert On Tue, Apr 3, 2012 at 6:25 PM, Melrose2012 <melissa.patric...@stonybrook.edu> wrote: > I am trying to plot the logistic regression of a dataset (# of living flies > vs days the flies are alive) and then fit a best-fit line to this data. > > Here is my code: > plot(fflies$living~fflies$day,xlab="Number of Days",ylab="Number of Fruit > Flies",main="Number of Living Fruit Flies vs Day",pch=16) > alive <- (fflies$living) > dead <- (fflies$living[1]-alive) > glm.fit <- glm(cbind(alive,dead)~fflies$day,family="binomial") > summary(glm.fit) > lines(sort(fflies$day),fitted(glm.fit) [order (fflies$day)],col = > "red",lwd=2) > lines(glm.fit,col = "red",lwd=2) > > My problem is that, while I am pretty sure that I did the 'glm' command > correctly, when I try to plot this as a best-fit line on my data, it does > not fit (clearly on a different scale somehow). > > Can anyone enlighten me about what I am doing wrong? Should I be scaling > one of these somehow? I've tried various types of scaling but nothing plots > the line on top of the plot (no matter which I scale). > > Thanks so much for whatever help you can give me! > > Cheers, > Melissa > > -- > View this message in context: > http://r.789695.n4.nabble.com/logistic-regression-tp4530651p4530651.html > Sent from the R help mailing list archive at Nabble.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. -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm ______________________________________________ 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.