Hello Chuck, many thanks for your advice. IŽll go through the package and see if IŽll manage to visualize the interaction effect this time as I already tried it with a special tool for displaying models with interaction terms in 3D. http://www.uni-oldenburg.de/landeco/Download/Software/LR_Mesh/LR_Mesh.htm but could not yield any plausible results. Hopefully this time... best regards Christian
> -----Ursprüngliche Nachricht----- > Von: Chuck Cleland <[EMAIL PROTECTED]> > Gesendet: 31.08.06 14:16:12 > An: Christian Jones <[EMAIL PROTECTED]> > CC: r-help@stat.math.ethz.ch > Betreff: Re: [R] need help with an interaction term > Christian Jones wrote: > > Hello! > > Iï¿œm fitting a model with glm(family binomial). The best model counts 9 > > Variables and includes an interaction term that was generated by the > > product of to continuous variables (a*b). All variables are correlated > > under a value of 0.7 (Spearman rank order) While the estimates of both main > > effects are negativ, the resulting interaction term is positiv. This change > > of sign makes it difficult to interpret the model and above all, is this > > perhaps due to a bad variable choice ? > > Thanks a lot for helping > > Rather than trying to interpret the model coefficients directly, you > might visualize the a*b interaction effect. The effects package by John > Fox is very useful for this: > > http://cran.r-project.org/doc/packages/effects.pdf > > > Christian > > > > _______________________________________________________________________ > > Viren-Scan für Ihren PC! Jetzt für jeden. Sofort, online und kostenlos. > > Gleich testen! http://www.pc-sicherheit.web.de/freescan/?mc=022222 > > > > ______________________________________________ > > 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 > > and provide commented, minimal, self-contained, reproducible code. > > -- > Chuck Cleland, Ph.D. > NDRI, Inc. > 71 West 23rd Street, 8th floor > New York, NY 10010 > tel: (212) 845-4495 (Tu, Th) > tel: (732) 512-0171 (M, W, F) > fax: (917) 438-0894 > ______________________________________________ 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 and provide commented, minimal, self-contained, reproducible code.
