[R] R: fractional factorial design in R

From: <statistical.model_at_googlemail.com>
Date: Tue 24 Jan 2006 - 07:19:56 EST


> Yes, you're right. For, say, a 3 x 5 design, one can do this in as few as
7
runs -- but only in general by some version of one-factor-at-a-time (OFAT) designs, which are inefficient. It is easy, via, say model.matrix() to write a general function to produce these. But I think it's a bad idea; more efiicient algorithmic designs are better, IMO, which is why I suggested AlgDesign. You and others are free to disagree, of course.

Hi Bert,
thanks for your suggestion.
However, let us say that i need a 2x2x2x3x3x3 design, which should not be too hard.
I've loaded AlgDesign, and i am aware now that gen.factorial allows me to create a full desing. But how to create a main-effects-only factorial design (orthogonal)?
I am still not able to produce what i need. The function model.matrix.formula is not very clear... :(

Could you please indicate which syntax should i use? I'd really appreciate your help.

Thanks in advance,

Roberto Furlan
University of Turin, Italy



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