On Wed, 8 Sep 2010, Paul Johnson wrote:
run it with factor() instead of ordered(). You don't want the
"orthogonal polynomial" contrasts that result from ordered if you need
to compare against Stata.
If you don't want polynomial contrasts for ordered factors, you can just tell R
not to use them.
options(contrasts=c("contr.treatment","contr.treatment"))
It's like the Good Old Days when you had to use options() to tell S-PLUS not to
use Helmert contrasts.
-thomas
Thomas Lumley
Professor of Biostatistics
University of Washington, Seattle
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