Dear Jeroen, It's true that the sem() function only handles quantitative endogenous variables, but you could use it along with functions in the polycor package to fit models with ordered or dichotomous observed variables. There's an example of a confirmatory factor analysis model with ordinal indicators in the paper at <http://socserv.mcmaster.ca/jfox/Misc/sem/SEM-paper.pdf>.
I hope this helps, John ------------------------------ John Fox, Professor Department of Sociology McMaster University Hamilton, Ontario, Canada web: socserv.mcmaster.ca/jfox > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Jeroen Ooms > Sent: July-27-08 2:52 PM > To: r-help@r-project.org > Subject: [R] Link functions in SEM > > > Is it possible to fit a structural equation model with link functions in R? I > am trying to build a logistic-regression-like model in sem, because > incorporating the dichotomous variables linearly seems inappropriate. Mplus > can do something similar by specifying a 'link' parameter, but I would like > to be able to do it in R, ofcourse. > > I have explored the 'sem' package from John Fox, but it does not seem to be > able to fit non-linear relations. Is there some R-package or way to get this > done? I have also considered creating a seperate latent variable in the sem > model for the systematic component of the predictors, but then I still need > a way to fix a non-linear link from the systematic component to the > dichotomous Y variable. > -- > View this message in context: http://www.nabble.com/Link-functions-in-SEM- > tp18679236p18679236.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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.
