I am pretty certain a function for this model does not exist. Jan Deleeuw or Dimitris Rizopolous may suggest otherwise. There is a package for a model that would allow for the lower asymptote of the function to be > 0; it does not however, allow the upper asymptote to vary from 1 (well, it tends to 1) and this is in the ltm package.
> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Mario Maiworm > Sent: Thursday, August 21, 2008 7:05 AM > To: r-help@r-project.org > Subject: [R] psychometric functions > > Hi, > I want to fit some psychophysical data with cumulative > gaussians. There is quite a convenient toolbox for matlab > called 'psignifit' (formerly known as 'psychofit'). It allows > the lower bound of the sigmoid to vary slightly from zero, > aswell as the upper bound to vary from one. with these two > free parameters, the fitted function is less sensitive to > noisy data and outliers. > Apart from advertising this toolbox I want to ask for > possibilities in R to fit psychometric functions, as I would > rather use R than matlab. Is there a comparable package > specific for psychophysics in R? otherwise: which function > would be a good choice? Can I have functionality equal to > 'psignifit' with glm() from MASS. I would be grateful for > some suggestions of people who have experience in > sigmoid-fitting in R. > Best, > Mario. > > > __________________________________________________________________ > > Mario Maiworm > Biological Psychology and Neuropsychology University of > Hamburg Von-Melle-Park 11 > D-20146 Hamburg > > Phone: +49 40 42838 8265 > Fax: +49 40 42838 6591 > > http://bpn.uni-hamburg.de/Maiworm_e.html > http://cinacs.org > > ______________________________________________ > 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. > ______________________________________________ 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.