pianka_var: PiankaVariance Niche Overlap Metric

In EcoSimR: Null Model Analysis for Ecological Data

Description

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

Usage

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

Arguments

m	a matrix of resource utilization values.

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.

Value

Returns the variance of the average pairwise niche overlap.

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.

See Also

pianka niche overlap index.

Examples

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

Example output

Loading required package: MASS

EcoSimR documentation built on May 2, 2019, 7:26 a.m.