  Walsh coefficients have been applied extensively to biallelic systems for
quantifying pairwise and higher order epistasis, in particular for
demonstrating the empirical importance of higher order interactions. Circuits,
or minimal dependence relations, and related approaches that use triangulations
of polytopes have also been applied to biallelic systems. Here we provide
biological interpretations of Walsh coefficients for several alleles, and
discuss circuits in the same general setting.
