Gamer, Matthias <gamer <at> uni-mainz.de> writes: > Specifically, I have data from a psychometric function relating the > frequency a subject's binary response (stimulus present / absent) to the > strength of a physical stimulus. Such data is often modeled using a > cumulative gaussian function.
Well, more often by a logistic function, and there are quite a few tools powerful for doings this around, for example glm, or lmer/lme4, glmmPQL/MASS, glmmML/glmmML . The latter three are the tools of choice when you have within subject repeats, as it's standard in psychophysics. See http://finzi.psych.upenn.edu/R/Rhelp02a/archive/33737.html for a comparison. If you really want a cumlative gaussian, you can misuse drfit/drfit, which is primarily for dose/response curves and ld50 determination. I think there is a fitdistr/MASS example around (somewhere in the budworms chapter), but I don't have the book at hand currently. Dieter ______________________________________________ [email protected] 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.
