affinity index A measure of the relative similarity of composition of two samples, e.g. , where a and b are the numbers of species in one sample but not in the other and vice versa respectively, and c is the number of species common to both. The reciprocal, , indicates the ecological and phytosociological distance (D) between samples.

affinity index A measure of the relative similarity in composition of two samples. For example, A = c/√(a + b), where A is the affinity index, a and b are the numbers of species in one sample but not in the other and vice versa respectively, and c is the number of species common to both. The reciprocal √(a + b)/c, indicates the ecological and phytosociological distance (D) between samples.

affinity index A measure of the relative similarity in composition of two samples. For example, A = c√(a + b), where A is the affinity index, a and b are the numbers of species in one sample but not in the other and vice versa respectively, and c is the number of species common to both. The reciprocal √(a + b)/c, indicates the ecological distance (D) between samples.