## Usage

sim4(speciesData)

## Arguments

- speciesData
- binary presence-absence matrix
(rows = species, columns = sites).

## Value

Returns a binary presence-absence matrix with the same
dimensions and rowsums as the input matrix.

## Description

Randomizes a binary matrix speciesData by reshuffling elements
within each row. Sampling weights for each column are proportional to
column sums. Makes a call to the vector_sample function.

## Details

This algorithm preserves differences among species in occurrence
frequencies, but assumes differences among sites in suitability are
proportional to observed species richness (= column sums).

## Note

This algorithm preserves differences in the commonness and rarity of
species (= rowsums), but assumes differences among sites in suitability are
proportional to observed species richness (= column sums). sim4 has a
somewhat high frequency of Type I errors with random matrices, so it is not
recommended for co-occurrence analysis.

## References

Gotelli, N.J. 2000. Null model analysis of species co-occurrence
patterns. Ecology 81: 2606-2621.

## Examples

randomMatrix <- sim4(speciesData = matrix(rbinom(40,1,0.5),nrow=8))