I don't know that you would be too far away from being able to use R from doing this. I haven't thought about this model, but if you could write out the likelihood, you *might* be able to use the MML procedures that is used for similar psychometric functions in ltm, which I think uses optim()
> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Mario Maiworm > Sent: Thursday, August 21, 2008 9:16 AM > To: r-help@r-project.org > Subject: Re: [R] psychometric functions > > Thank you harold. Hmm thats bad news. I will have a look at > the LTM package but right now I feel like I should lean back > and use matlab, and then get the fit results into R for > further analyses... > 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 > __________________________________________________________________ > > >>> -----Original Message----- > >>> From: Doran, Harold [mailto:[EMAIL PROTECTED] > >>> Sent: Thursday, August 21, 2008 2:40 PM > >>> To: Mario Maiworm; r-help@r-project.org > >>> Subject: RE: [R] psychometric functions > >>> > >>> 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. > ______________________________________________ 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.
