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choosedef2(k,p, all:T  or  tries:m), k, p, m > 0 integer scalars

Keywords: confounding, design, factorial
choosedef2(k, p, all:T) searches all potential defining contrasts to
find a set for a 2^k factorial design in 2^p blocks.  k must be an
integer between 1 and 32 and p an integer < k.

choosedef2(k,p,tries:m) does the same, except only m random sets of
defining contrasts are searched.

In both cases, the defining contrasts for the minimum aberration design
among those searched is returned.

The return value is
  structure(generators:bestgen, aberration:aber, basis:genmat).

bestgen is a CHARACTER vector of length p with the names such as "ABDF"
of the defining contrasts in the set chosen.

aber is a vector of k integers >= 0 with ab[i] containing the number
of contrast with i letters that are confounded with "I".

genmat is a p by k matrix with entries 0 and 1, one row for each element
of bestgen.  genmat[i,j] is 1 if and only if factor j is bestgen[i].
For example, if bestgen[i] is "ABDF", genmat[i,] is vector(1,1,0,1,0,1
[,...])'.  genmat can be used as an argument to aliases2() to determine
all the aliases of any contrast.

See also aliases2() choosegen2(), confound2().

Gary Oehlert 2003-01-15