>Dear all R-users, > >I am a new user of R and I am trying to build a discrete choice model (with >more than two alternatives A, B, C and D) using logistic regression. I have >data that describes the observed choice probabilities and some background >information. An example below describes the data: > >Sex Age pr(A) pr(B) pr(C) pr(D) ... >1 11 0.5 0.5 0 0 >1 40 1 0 0 0 >0 34 0 0 0 1 >0 64 0.1 0.5 0.2 0.2 >...
You can use multinom() Here is an exemple For example let this matrix to be analyzed: male female aborted factor 10 12 1 1.2 14 14 4 1.3 15 12 3 1.4 The data are to be entered in a text file like this: output factor n m 1.2 10 f 1.2 12 a 1.2 1 m 1.3 14 f 1.3 14 a 1.3 4 m 1.4 15 f 1.4 12 a 1.4 3 library(MASS) dt.plr <- multinom(output ~ factor, data=dt, weights=n, maxit=1000) dt.pr1<-predict(dt.plr, , type="probs") dt.pr1 >I have been able to model a case with only two alternatives "A" and "not A" >by using glm(). > >I do not know what functions are available to estimate such a model with >more than two alternatives. Multinom() is one possibility, but it only >allows the use of binary 0/1-data instead of observed probabilities. Did I >understand this correctly? > >Additionally, I am willing to use different independent variables for the >different alternatives in the model. Formally, I mean that: >Pr(A)=exp(uA)/(exp(uA)+exp(uB)+exp(uC)+exp(uD) >Pr(B)=exp(uB)/(exp(uA)+exp(uB)+exp(uC)+exp(uD) >... >where uA, uB, uC and uD are linear functions with different independent >variables, e.g. uA=alpha_A1*Age, uB=alpha_B1*Sex. > >Do you know how to estimate this type of models in R? I don't think it is possible... (at least simply, without writing all the script !) Note that I don't undrestand where the residual deviance from multinom() come from. I cant find the logic. Marc -- __________________________________________________________ Marc Girondot, Pr Laboratoire Ecologie, Systématique et Evolution Equipe de Conservation des Populations et des Communautés CNRS, ENGREF et Université Paris-Sud 11 , UMR 8079 Bâtiment 362 91405 Orsay Cedex, France Tel: 33 1 (0)1.69.15.72.30 Fax: 33 1 (0)1 69 15 56 96 e-mail: [EMAIL PROTECTED] Web: http://www.ese.u-psud.fr/epc/conservation/Marc.html Skype: girondot Fax in US: 1-425-732-6934 ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
