[R] simple interactions
Therneau, Terry M., Ph.D.
therneau at mayo.edu
Fri Apr 15 15:42:56 CEST 2016
I was right that there is an easy answer!
Thanks for the 3 quick answers, all three correct and useful.
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
>> 2016-04-15 13:58 GMT+02:00 Therneau, Terry M., Ph.D. <therneau at mayo.edu
> <mailto:therneau at mayo.edu>>:
> 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 course). The coefficients of the model will
> then be the age effect in group A, the age effect in group B and the age effect in C
> rather than the standard ones of an overall age effect followed by contrasts. These
> is often a better format for tables in a publication.
> Yes, I can reconstruct these from the original fit, but I have a lot of variables for
> several models and it would be easier to have an automatic form. I suspect that there
> is an easy answer, but I don't see it.
> Terry Therneau
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