Calculate Simpson's Diversity Index

This function calculates Simpson's diversity index, which measures the probability that two individuals randomly selected from a sample will belong to different species.

simpson(x)

Arguments

x

A character vector of species names. Each element represents an individual of a species.

Value

A numeric value representing Simpson's diversity index. Returns NA if the input vector is empty or contains fewer than two unique species.

Note

Simpson's index is undefined for an empty vector or vectors with only one unique species. The function will return NA in such cases with a warning.

Examples

# Example 1: Calculate Simpson's diversity index
x <- c("jonesi","gambiensis","hispida","hispida","thebaica","helvum","helvum","gambianus","gambianus","pusillus","monstrosus","aegyptiacus")
simpson(x)
#> [1] 8

# Example 2: Handle edge cases
simpson(c("pusillus")) # Returns NA with a warning
#> Warning: Simpson's index is undefined for fewer than 2 species. Returning NA.
#> [1] NA
simpson(character(0)) # Returns NA with a warning
#> Warning: Input vector is empty. Returning NA.
#> [1] NA