ra1: RA1 Niche Overlap Randomization Algorithm
In EcoSimR: Null Model Analysis for Ecological Data

Description Usage Arguments Details Value Note References Examples

Randomizes a numeric utilization matrix speciesData by replacing all elements with a random uniform [0,1] value.

1	ra1(speciesData = matrix(rpois(80, 1), nrow = 10))

speciesData

a resource utilization matrix (rows = species, columns = discrete resource states) filled with non-negative real numbers.

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.

Returns a random utilization matrix with the same dimensions as the input matrix.

Because all matrix elements, including zeroes, are replaced with a random uniform distribution, the null expectation is based on an assemblage of generalist species with maximum niche breadth. This algorithm retains neither the niche breadth of the individuals species nor the placement of 0 values (= unutilized resource states) in the matrix. These assumptions are unrealistic, and a random matrix with zeroes will generate significantly low niche overlap values with this metric. It is not recommended for niche overlap analysis.

Kobayashi, S. 1991. Interspecific relations in forest floor coleopteran assemblages: niche overlap and guild structure. Researches in Population Ecology 33: 345-360.