Takes a binary presence-absence matrix and returns the skewness of the Stone and Roberts' (1990) C-score.
a binary presence-absence matrix in which rows are species and columns are sites.
A large positive value of skewness implies a preponderance of species pairs with large C-score values (segregated), whereas a large negative value of skewness implies a preponderance of species pairs with small C-score values (aggregated).
Returns the skewness of the C-score calculated across all possible species pairs in the matrix.
The matrix-wide C-score is not calculated for missing species, so empty rows in the matrix do not affect the result. This index has not been thoroughly tested with real data sets.
Stone, L. and A. Roberts. 1990. The checkerboard score and species distributions. Oecologia 85: 74-79.
Stone, L. and A. Roberts. 1992. Competitive exclusion, or species aggregation? An aid in deciding. Oecologia 91: 419-424.
c_score co-occurrence index.