Stanislav Aggerwal <stan.aggerwal <at> gmail.com> writes: > > I have the following problem. > DV is binomial p > IV is quantitative variable that goes from negative to positive values. > > The data look like this (need nonproportional font to view):
[snip to make gmane happy] > If these data were symmetrical about zero, > I could use abs(IV) and do glm(p > ~ absIV). > I suppose I could fit two glms, one to positive and one to negative IV > values. Seems a rather ugly approach. > [snip] What's wrong with a GLM with quadratic terms in the predictor variable? This is perfectly respectable, well-defined, and easy to implement: glm(y~poly(x,2),family=binomial,data=...) or y~x+I(x^2) or y~poly(x,2,raw=TRUE) > (To complicate things further, this is within-subjects design) glmer, glmmPQL, glmmML, etc. should all support this just fine. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
