Greetings, I am working on a logistic regression model in R and I am struggling with the code, as it is a relatively new program for me. In searching Google for 'logistic regression diagnostics' I came Elizabeth Brown's Lecture 14 from her Winter 2004 Biostatistics 515 course (http://courses.washington.edu/b515/l14.pdf) . I found most of the code to be very helpful, but I am struggling with the lines on to calculate the observed and expected values in the 10 groups created by the cut function. I get error messages in trying to create the E and O matrices: R won't accept assignment of "fi1c==j" and it won't calculate the sum.
I am wondering whether someone might be able to offer me some assistance...my search of the archives was not fruitful. Here is the code that I adapted from the lecture notes: fit <- fitted(glm.lyme) fitc <- cut(fit, br = c(0, quantile(fit, p = seq(.1, .9, .1)),1)) t<-table(fitc) fitc <- cut(fit, br = c(0, quantile(fit, p = seq(.1, .9, .1)), 1), labels = F) t<-table(fitc) #Calculate observed and expected values in ea group E <- matrix(0, nrow=10, ncol = 2) O <- matrix(0, nrow=10, ncol=2) for (j in 1:10) { E[j, 2] = sum(fit[fitc==j]) E[j, 1] = sum((1- fit)[fitc==j]) O[j, 2] = sum(pcdata$lymdis[fitc==j]) O[j, 1] = sum((1-pcdata$lymdis)[fitc==j]) } Here is the error message: Error in Summary.factor(..., na.rm = na.rm) : sum not meaningful for factors I understand what it means; I just can't figure out how to get around it or how to get the output printed in table form. Thank you in advance for any assistance. Mary Sullivan ______________________________________________ R-help@stat.math.ethz.ch 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.