[R] how to adjust link function in logistic regression to predict the proportion of correct responses in 2AFC task?
Prof Brian Ripley
ripley at stats.ox.ac.uk
Sat Dec 16 07:01:15 CET 2006
On Sat, 16 Dec 2006, baud-bovy.gabriel at hsr.it wrote:
> I have would like to use logistic regression to analyze the
> percentage of correct responses in a 2 alternative forced
> choice task. The question is whether one needs to take into
> account the fact expected probabilities for the percentage of
> correct responses ranges between 0.5 and 1 in this case.
Yes.
> Second, how can one implement a link function of the
> type f(x) = (1+exp(x)/(1+exp(x)))/2 in R?
Looking at make.link() should give you enough to go on.
> Third, can it be also done with gee and/or glmm?
For gee, you need to change the C-level internals. (I've done this in the
far past for S-PLUS but not for R.) It would be easier to use yags (but I
think you still need to dive into the internals).
What 'glmm' did you have in mind? Looks like e.g. glmmML and glmmPQL will
work with the new link.
[...]
Someone may have been here already: e.g.
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1434755
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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