Re: [R] simple interactions

> Therneau, Terry M , Ph D > on Fri, 15 Apr 2016 06:58:22 -0500 writes: > I'd like to get interaction terms in a model to be in > another form. Namely, suppose I had variables age and > group, the latter a factor with levels A, B, C, with age * >

Re: [R] simple interactions

I was right that there is an easy answer! Thanks for the 3 quick answers, all three correct and useful. Terry Therneau On 04/15/2016 07:15 AM, Thierry Onkelinx wrote: Dear Terry, Does fitting group + age:group instead of age*group solves your problem? Best regards, ir. Thierry Onkelinx

Re: [R] simple interactions

Try using ~ group/age or even ~ 0 + group/age Both have all three group-specific slopes but differ with respect to the intercept codings. The latter has three group-specific intercepts as well. But the former has an intercept corresponding to the reference group A and then the usual

Re: [R] simple interactions

Dear Terry, Does fitting group + age:group instead of age*group solves your problem? Best regards, ir. Thierry Onkelinx Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance Kliniekstraat 25 1070

[R] simple interactions

I'd like to get interaction terms in a model to be in another form. Namely, suppose I had variables age and group, the latter a factor with levels A, B, C, with age * group in the model. What I would like are the variables "age:group=A", "age:group=B" and "age:group=C" (and group itself of