Random null model
Null model based on randomization of locations as suggested by Raes and ter Steege (2007).
nullRandom(x, model, n=25, rep=25, pa=FALSE)
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) |
List with n object of class ModelEvaluation-class
Robert J. Hijmans
Raes, N. & H. ter Steege, 2007. A null-model for significance testing of presence-only species distribution models. Ecography 30:727-736.
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))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.