[R] Fitting a cumulative gaussian

From: Gamer, Matthias <gamer_at_uni-mainz.de>
Date: Fri 06 Oct 2006 - 09:49:38 GMT


Dear R-Experts,

I was wondering how to fit a cumulative gaussian to a set of empirical data using R. On the R website as well as in the mail archives, I found a lot of help on how to fit a normal density function to empirical data, but unfortunately no advice on how to obtain reasonable estimates of m and sd for a gaussian ogive function.
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. I have tried to implement such a fitting algorithm in R, but unfortunately, I was not successful. Maybe anyone on the list already coded a script for such purposes or could help me otherwise???

Thanks in advance,
Matthias



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