On 14-Jul-03 Z Eric wrote: > Hi, I want to know is there other functions in R to > estimate qualitative response model besides multinom() > in library nnet, if this is the only possibility, I > have a question about the application: > for example: > there is three transportation choice : car, bus, subway. > each alternative has own characteristic variables, > I want to apply conditional logit model to analysis > the choice of three alternatives, but if some cases > face different choice set, i.e only car and bus are > available, how to use this function? > I am a newcomer in R, hope the simple question not to > bother you. > thanks for the help.
A totally naive idea would be to incorporate the "choice" set as a set of three factors CAR=0/1, BUS=0/1, SUB=0/1 according to availability. Naively, since (e.g.) CAR=0 would lead to zero cases observed, one might expect that the estimation would predict zero for these. However, in conjunction with the logistic model the parameter estimates would be improper (-> inf). Nevertheless, there may be some mileage in an approach which incorporated this idea, though I'm not seeing how! If it could be got to work, though, it should lead to a convenient representation of interesting interactions, e.g. how does propensity to use "car" change if "subway" is not available? Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 167 1972 Date: 14-Jul-03 Time: 14:14:22 ------------------------------ XFMail ------------------------------ ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
