# RA4 Niche Overlap Randomization Algorithm

### Description

Randomizes a numeric utilization matrix speciesData by reshuffling the non-zero elements within each row.

### Usage

1 |

### Arguments

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

### Details

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.

### Value

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

### Note

This algorithm is similar to RA3, but adds the additional constraint of retaining the positions of all of the zero elements of the matrix, and reshuffling only the non-zero elements of the matrix within each row. It is more conservative than RA3, but has a low Type I error rate, and, along with RA3, is recommended for null model analysis of niche overlap.

### 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

1 |