Fractional Factorial Design
H = scidoe_fracfact(gen)
a 1-by-n matrix of strings, consisting of lowercase ,uppercase letters or operators "-" and "+", indicating the factors of the experiment
a m-by-n matrix of doubles, the fractional factorial design. m is 2^k, where k is the number of letters in gen, and n is the total number of entries in "gen"
The function computes a fractional factorial design. Fractional factorial designs are used instead of full factorial designs, because they need fewer runs.
In "gen" we define the main factors of the experiment and the factors whose levels are the products of the main factors. For example, if
gen = "a b ab"
For example, if
gen = "a b -ab"
The output matrix includes a two level full factorial design, built by the main factors of gen, and the products of the main factors. The columns of H follow the sequence of "gen". For example, if
gen = "a b ab c"
http://www.itl.nist.gov/div898/handbook/pri/section3/pri3342.htm
http://www.mathworks.com/help/toolbox/stats/fracfact.html