[R] simple interactions
Therneau, Terry M., Ph.D.
therneau at mayo.edu
Fri Apr 15 13:58:22 CEST 2016
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.
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