choosegen2(k,p, all:T [,res:r]), positive integers k, p, r. choosegen2(k,p, tries:m [,res:r]), positive integers k, p, m, and r. |

choosegen2(k,p,all:T) , where k, p and r are positive integers, searches all potential sets of generators for a 2^(k-p) fractional factorial design. It returns information on a generator with maximum resolution. choosegen2(k,p, tries:m), where m > 0 is an integer, does the same, except it searches only m randomly selected sets of generators. choosegen2(k,p,all:T,res:r) and choosegen2(k,p,tries:m,res:r), where r is a positive integer, do the same, except they stop the search at the first design of resolution r. If none is found, they return information on a set having the highest resolution found. The value returned is structure(resolution:bestres,generators:bestgen,aberration:aber,\ basis:genmat) Integer bestres > 0 is the best resolution found. 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. Examples: Cmd> choosegen2(5,2,all:T) # find best resolution component: resolution (1) 3 component: generators (1) "ABCD" (2) "BCE" component: aberration (1) 0 0 2 1 0 component: basis (1,1) 1 1 1 1 0 (2,1) 0 1 1 0 1 Cmd> choosegen2(5,2,all:T,res:4) # try to find 4 (we won't) component: resolution (1) 3 component: generators (1) "ABCD" (2) "BCE" component: aberration (1) 0 0 2 1 0 component: basis (1,1) 1 1 1 1 0 (2,1) 0 1 1 0 1 Cmd> # look for 2^(9-4) resol. 4, just make 1000 tries, since\ there are lots of combinations to explore Cmd> choosegen2(9,4,tries:1000,res:4)# look for 2^(9-4) resol. 4 component: resolution (1) 4 component: generators (1) "CDEF" (2) "BDEG" (3) "ABCEH" (4) "BCDJ" component: aberration (1) 0 0 0 7 7 (6) 0 0 0 1 component: basis (1,1) 0 0 1 1 1 (1,6) 1 0 0 0 (2,1) 0 1 0 1 1 (2,6) 0 1 0 0 (3,1) 1 1 1 0 1 (3,6) 0 0 1 0 (4,1) 0 1 1 1 0 (4,6) 0 0 0 1 See also aliases2(), choosedef2(), confound2().

Gary Oehlert 2003-01-15