>>>>> On Wed, 29 Jan 2003 11:57:20 -0800 (PST), >>>>> John Hendrickx (JH) wrote:
> A multinomial logit model can be specified as a conditional logit > model after restructuring the data. Doing so gives flexibility in > imposing restrictions on the dependent variable. One application is > to specify a loglinear model for square tables, e.g. quasi-symmetry > or quasi-independence, as a multinomial logit model with covariates. > Further details on this technique and examples with several packages > are on my homepage at http://www.xs4all.nl/~jhckx/mcl/ > I've been trying to implement an MCL model in R and have been mostly > succesful. However I'm still stuck on a few points and I'm hoping > someone can point out how to do fix them. > To estimate an MCL model, the data must be restructured into a > person-choice file. > * Each case must be duplicated "ncat" times ("ncat" is the number of > categories of the dependent variable) > * Each case must be identified by a strata variable (id) > * Each duplicate must be identified by a variable indexing the > choices (newy) > * A dichotomous variable must indicate which duplicate corresponds > with the respondent's choice (didep) I'm not completely sure if I understand your target format completely, but it sounds like reshape() could do all you want: R> df3 id age dose1 dose2 dose4 1 1 40 1 2 3 2 2 50 2 1 3 3 3 60 1 2 3 4 4 50 2 1 3 R> reshape(df3, direction = "long", idvar=1, varying=list(dose=c("dose1", "dose2", "dose4"))) id age time dose1 1.1 1 40 1 1 2.1 2 50 1 2 3.1 3 60 1 1 4.1 4 50 1 2 1.2 1 40 2 2 2.2 2 50 2 1 3.2 3 60 2 2 4.2 4 50 2 1 1.3 1 40 3 3 2.3 2 50 3 3 3.3 3 60 3 3 4.3 4 50 3 3 which is a (modified) example from help(reshape) ... there you find much more examples. Hope this helps, Fritz -- ------------------------------------------------------------------- Friedrich Leisch Institut für Statistik & DSS Tel: (+43 1) 4277 38613 Universität Wien Fax: (+43 1) 4277 38639 Universitätsstraße 5 [EMAIL PROTECTED] A-1010 Wien, Austria http://www.ci.tuwien.ac.at/~leisch ------------------------------------------------------------------- ______________________________________________ [EMAIL PROTECTED] mailing list http://www.stat.math.ethz.ch/mailman/listinfo/r-help
