For each unique pair of species, the C-score is calculated as$$C_{ij} = (R_i - S)(R_j - S)$$
where R_i and R_j are the row sums for species i and j, and S is the number
of shared sites in which both species i and species j are present. For any
particular species pair, the larger the C-score, the more segregated the
pair, with fewer shared sites. However, the index can be difficult to
interpret when calculated as a matrix-wide average, because a single matrix
can contain individual pairs of species that are segregated, random, or aggregated.
Degenerate matrices result from simulations where a row or column sum may be 0.