Jost diversity index

**See also
**alpha_div command

Alpha diversity metrics

Effective number of species

In a 2010 paper, Chao, Chui and Jost describe a family of metrics
based on Hill numbers with a single
parameter (*q*) that determines how abundance is weighted. I call these Jost indexes of order *q*.
The numerical value of the metric for any *q* is an
effective number of species.

The parameter *q* is the
power to which the species frequencies are raised. Higher values of *q *
thus give lower weights to low-abundance species. With *q*=0 the Jost
index is exactly equivalent to richness. With *q*=1, the Jost index is the
effective number of species given by the Shannon entropy. The *q*
parameter can take real values, not just integers, which allows intermediate
metrics with different weightings of abundance.

**Reference**
Chao,
Chui and Jost (2010)