Simpson Dominance Index

## Usage

```
index_simpson(x, ...)
# S4 method for numeric
index_simpson(x, evenness = FALSE, unbiased = FALSE, na.rm = FALSE, ...)
```

## Value

A `numeric`

vector.

## Details

The Simpson index expresses the probability that two individuals randomly picked from a finite sample belong to two different types. It can be interpreted as the weighted mean of the proportional abundances. This metric is a true probability value, it ranges from \(0\) (all taxa are equally present) to \(1\) (one taxon dominates the community completely).

This is a *dominance* index, so that an increase in the value of the index
accompanies a decrease in diversity.

## References

Simpson, E. H. (1949). Measurement of Diversity. *Nature*, 163(4148),
688-688. doi:10.1038/163688a0
.

## See also

Other alpha diversity measures:
`index_ace()`

,
`index_baxter()`

,
`index_berger()`

,
`index_boone()`

,
`index_brillouin()`

,
`index_chao1()`

,
`index_chao2()`

,
`index_hurlbert()`

,
`index_ice()`

,
`index_margalef()`

,
`index_mcintosh()`

,
`index_menhinick()`

,
`index_shannon()`

,
`index_squares()`