## Usage

pianka_var(m = matrix(rpois(80, 1), nrow = 10))

## Arguments

- m
- a matrix of resource utilization values.

## Value

Returns the variance of the average pairwise niche overlap.

## Description

Takes a niche utilization matrix as in put and
returns the variance of Pianka's niche overlap index.

## Details

A large value for variance implies that some species pairs show high
niche overlap and others show low niche overlap. A low value for variance
implies that niche overlap (high or low) is very similar among all species pairs.

## Note

The resource utilization matrix (rows = species, columns = discrete
resource categories) may include zeroes, but no negative numbers or missing
values. Relative resource within a species is first calculated, so the rows
need not sum to 1.0.

## References

Winemiller, K.O. and E.R. Pianka. 1990. Organization in natural
assemblages of desert lizards and tropical fishes. Ecological Monographs 60:
27-55.

## Examples

obsVar <- pianka_var(m=matrix(rpois(40,0.5),nrow=8))