Hi Folks, According to the PDF file blogit.pdf in the Zelig documentation: "Use the bivariate logistic regression model ["blogit"] if you have two binary dependent variables (Y1,Y2), and and wish to model them jointly as a function of some explanatory variables. Each pair of dependent variables (Yi1,Yi2) has four potential outcomes, (Yi1=1,Yi2=1), (Yi1=1,Yi2=0), (Yi1=0,Yi2=1), and (Yi1=0,Yi2=0). The joint probability for each of these four outcomes is modeled with three systematic components: the marginal Pr(Yi1=1) and Pr(Yi2=1), and the odds ratio psi, which describes the dependence of one marginal on the other. Each of these systematic components may be modeled as functions of (possibly different) sets of explanatory variables."
I want to do precisely that: Model two joint binary responses Y1 and Y2, AND their odds ratio, in terms of explanatory variables (categorical as it happens) A and B. I cannot make out, from any of the documentation, how to formulate this in Zelig. The Zelig documentation does not state a comprehensive syntax, and there are no examples shown in which this (fitting OR as well as marginals) is illustrated. I can readily imitate the examples given, and obtain a fit to (Y1,Y2) but only with a constant psi over all combinations of the explanatories. On the other hand, if I try to guess at how to fit the OR as well, I either get a non-specific error or I am told that I can only supply two models and I have supplied three. Can anyone help by stating the syntax for fitting the OR as well as the marginals? Or might it be the case that, despite the above citation, it in fact can not be done? With thanks, Best wishes, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 094 0861 Date: 01-Nov-07 Time: 12:11:03 ------------------------------ XFMail ------------------------------ ______________________________________________ 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.
