strong {abdiv}

Strong's dominance index

Description

Strong's dominance index measures the maximum departure between the observed proportions and a perfectly even community.

Usage

strong(x)

Arguments

x

A numeric vector of species counts.

Details

Strong's dominance index is defined as

D_W = \max_i \left [ \frac{b_i}{N} - \frac{i}{S} \right ],

where b_i is the abundance of the ith species, ordered from smallest to largest, N is the total number of counts, and S is the number of species observed.

Equivalent to strong() in skbio.diversity.alpha.

Value

Strong's dominance index, 0 \leq D_W < 1. The index is undefined if x sums to 0, and we return NaN in this case.

References

Strong WL. Assessing species abundance uneveness within and between plant communities. Community Ecology. 2002;3:237-246.

Examples

x <- c(9, 0, 1, 2, 5, 2, 1, 1, 0, 7, 2, 1, 0, 1, 1)
strong(x)