Random null model {dismo}

Random null model

Description

Null model based on randomization of locations as suggested by Raes and ter Steege (2007).

Usage

nullRandom(x, model, n=25, rep=25, pa=FALSE)

Arguments

x

data.frame with environmental predictor values for collecting localities

model

Model function that creates a model of class 'DistModel'

n

Sample size

rep

Number of repetitions

pa

Boolean. Prensence-only or presence/background model (e.g. Maxent)

Value

List with n object of class ModelEvaluation-class

Author(s)

Robert J. Hijmans

References

Raes, N. & H. ter Steege, 2007. A null-model for significance testing of presence-only species distribution models. Ecography 30:727-736.

See Also

geoDist

Examples

predictors <- stack(list.files(path=paste(system.file(package="dismo"), '/ex', sep=''), 
               pattern='grd', full.names=TRUE ))
occurence <- paste(system.file(package="dismo"), '/ex/bradypus.csv', sep='')
occ <- read.table(occurence, header=TRUE, sep=',')[,-1]
 
x <- extract(predictors, occ)
nr <- nullRandom(x, bioclim, n=25, rep=25, pa=FALSE)
mean(sapply(nr, function(x)x@auc))