randtest.enfa {adehabitat} | R Documentation

## Randomisation Test for the Ecological Niche Factor Analysis

### Description

`randtest.enfa` performs a randomisation test for the Ecological Niche Factor analysis (ENFA).

### Usage

    randtest.enfa(xtest, nrepet = 999, ...)

### Arguments

`xtest` | an object of class `enfa`
`nrepet` | the number of iterations for the randomisation test
`...` | further arguments to be passed to the generic function `randtest`

### Details

This test is carried out by simulating a random distribution of the species occurrences in the pixels of a map.

At each step of the randomisation procedure, the test randomly allocates the nk occurrences (where nk is the sum of the occurrence vector `pr` of the object of class `enfa`) in the Ik pixels of the focus area (where Ik is the length of this occurrence vector).

At each step of the procedure, the first eigenvalue of the ENFA performed on the randomised data set is recomputed. This value provides a criterion to test the pertinence of the ENFA analysis.

### Value

returns a list of class `randtest`

### Author(s)

Clément Calenge calenge@biomserv.univ-lyon1.fr

### References

Manly, B.F.J. (1997) Randomization, Bootstrap and Monte Carlo Methods in Biology. London: Chapman & Hall.

Hirzel, A.H., Hausser, J., Chessel, D. and Perrin, N. (2002) Ecological-niche factor analysis: How to compute habitat suitability maps without absence data? Ecology, 83, 2027–2036.

### See Also

`enfa`

### Examples

    ## Not run:
    data(chamois)
    locs <- chamois$locs
    map <- chamois$map
    map$Vegetation <- NULL
    en <- enfa(map, locs, scannf=F)
    (tutu <- randtest(en))
    plot(tutu)
    ## End(Not run)

[Package adehabitat version 1.3 Index]