Ben> Help!!
Ben> Does anybody know an easy way of getting SAS like type III sums of
Ben> squares in S+?
This is almost an FAQ. The two rules are
1. Use contr.poly, contr.helmert or contr.sum contrast options for factors,
but *not* contr.treatment,
2. Use drop1(.,.) with a specific scope argument:
eg
> options(contrasts=c("contr.helmert", "contr.poly") # the default, but
> # make sure
> fm <- aov(y ~ A*B*C + x, data=my.data) # or whatever...
> drop1(fm, . ~ .)
Disclaimer: My considered opinion is that Type III sums of squares for
non-marginal terms, such as main effects with interactions involving them
are still present in the model, are very often of no interest whatever.
Bill
-- ___________________________________________________________________________ Bill Venables, Department of Statistics, Telephone: +61 8 303 3026 The University of Adelaide, Facsimile: +61 8 232 5670 South AUSTRALIA. 5005. Email: venables@stats.adelaide.edu.au