[Rd] how to exclude terms preceded by - from model frame

[Liaw, Andy]

[I believe few users manipulate formulae and model frames like this, so
I'm posting here instead of R-help.]

I just found out that model.frame() includes all terms, including those
preceded by "-" in the formula, in its output (as mentioned on its help
page).  Is there a recommended way of excluding "negative" terms?  My
guess is that I can use info in the terms attribute to figure this out,
but that doesn't seem very straightforward.  Any pointer would be much
appreciated.

Best,
Andy

Andy Liaw, PhD
Biometrics Research    PO Box 2000 RY33-300
Merck Research Labs        Rahway, NJ 07065
andy_liaw(a)merck.com          732-594-0820



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