strong {abdiv} | R Documentation |

## 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 `i`

th 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)
```

[Package

*abdiv*version 0.2.0 Index]