[R] R stepping through multiplie interactions

[Chuck Cleland]

On 1/23/2009 12:44 PM, ppeetteerr wrote:
> I have a lm in R in the form
> model <- lm( Z ~ A*B*C*D,data=mydata)
> I want to run the model and include all interactions expect the 4 way
> (A:B:C:D) is there an easy way of doing this? I then want to step down the
> model eliminating the non-significant terms I understand step() does this
> but how would I do it by hand?

  For the first part, try this:

lm(Z ~ (A + B + C + D)^3, data = mydata)

-- 
Chuck Cleland, Ph.D.
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