[Rd] contrasts

Torsten Hothorn Torsten.Hothorn at rzmail.uni-erlangen.de
Wed May 7 17:57:58 MEST 2003


I spent some time now trying to understand how functions for the
computation of contrasts

contr.foo(n, contrasts=TRUE)

passed to model.matrix are called. My problem is
that for the computation of some contrasts one needs `n' to be the number
of observations at each level of the factor of interest and for others the
number of levels is sufficient. For example, `contr.treatment' has code
for handling vector valued `n' (and ?contrasts states that `n' may be a vector).

Where can I find the condition under which `n = nlevel(x)' or `n =
table(x)' or how can I define what I would like to see?



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