[R] Generating Interaction Factors (combinations of Data Frame columns)

[Kjetil Brinchmann Halvorsen]

Thomas Hopper wrote:

> I'm starting to do a fair amount of DOE in my day job and need to 
> generate full- and fractional-factorial designs.
>
> One of the things I'd like to do is generate all possible interaction 
> effects, given the main effects. I've been searching through the 
> documentation, packages and mail list archives, but the closest I can 
> find are combin() in package combinat and combine() and combinations() 
> in gregsmisc, none of which actually produces the results I want.
>
> Given a data frame with columns labeled A, B, C and D, I would like to 
> generate a data frame with columns that are the combination of each of 
> the columns in the original data frame. The output columns would be 
> A*B, A*C, A*D, A*E, A*B*C, A*B*D,..., A*B*C*D.
>
> Alternatively, I'd want to generate the interactions for a given level 
> (2-factor or 3-factor).
>
> If such a function already exists, I'd be more than happy to use it.
>
> If it doesn't, I can write it, but I would appreciate a little help 
> with the algorithm for generating the combinations...how do I loop 
> through the given factors to generate all possible combinations?
>
> Thanks,
>
> Tom
>
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>
library(BHH2) # on CRAN
?ffDesMatrix
?ffFullMatrix

-- 

Kjetil Halvorsen.

Peace is the most effective weapon of mass construction.
               --  Mahdi Elmandjra





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