Sheldon's index is defined as \(S=\frac{e^H}{N}\), where H is the Shannon diversity and N the species number. It ranges from 0 to 1, where 1 signifies a perfectly even abundance distribution.
sheldon(x, correction = TRUE, N2N1 = FALSE)
x | a vector of species abundances |
---|---|
correction | whether or not to apply the correction described in Alatalo, Oikos 37, 199-204, 1981 |
N2N1 | whether to compute Sheldon's evenness as the ratio of e raised to the power of H (H = Shannon diversity) and Simpson's diversity |
Sheldon's evenness
Note that the N2N1 mode results in evenness smaller than 1 for equal taxon probabilities.
A.L. Sheldon 1969. Equitability indices: dependence on the species count. Ecology, 50, 466-467.
C Heip 1974. A new index measuring evenness. J. mar. biol. Ass. UK 54, 555-557.
#> [1] 0.6743761#> [1] 1#> [1] 0.009179405