[R] specifying models ":" and %in% and soforth

Daniel Lakeland dlakelan at street-artists.org
Mon Oct 15 02:08:15 CEST 2007


If a and b are factor variables are there any differences between 

~ a:b
~ b:a 
~ a %in% b
~ b %in% a

playing with model.matrix doesn't show any differences in the
resultant matrices, which is what I expect based on my understanding
if what's being specified.

I'm hoping that someone can clarify what (if any) the differences are.

Thanks,
Dan

-- 
Daniel Lakeland
dlakelan at street-artists.org
http://www.street-artists.org/~dlakelan



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