elsa.test: Elsa test for local spatial autocorrelation

In elsa: Entropy-based Local indicator of Spatial Association

Description

This function can be used to convert a data.frame including the values specifying the differences (digree of dissimilarities) between the classes (categories) in a categoricl map, to a list.

Usage

elsa.test(x, d, n, method, null, nc, categorical, dif,...)

Arguments

x	A Raster or Spatial* dataset
d	the local distance, or an object of class neighbours created by dneigh function
n	number of simulation, default is 999 for small datasets, and 99 for large datasets
null	Optional, a null distribution of data (a Raster if x is Raster or a numerical vector if x is either Raster or Spatial dataset ); if not provided, a null distribution is generated by the function
method	resampling method for nonparametric simulation, can be either 'boot' (bootstraping; default) or 'perm' (permutation)
nc	number of classes (only if x is a continuous variable); if not specified, it is estimated using nclass function
categorical	logical, specifies whether x is a categorical; if not specified, it is guessed by the function
dif	the level of dissimilarities between different categories (only if x is a categorical variable); see dif2list for more details
...	Aditional arguments passed to writeRaster function (applied only when x is Raster)

Details

This function test how significant the local spatial autocorrelation is at each location, so it generates a p-value at each location through a Monte Carlo simulation and a non-parametric approach. See the reference for the details about the method.

If null distribution is not provided, the function generates a null distribution by drawing a sample at each location from a unique set of m values in dataset (categories) each having a probability of 1/m.

Value

An object same as the input (x)

Author(s)

Babak Naimi [e-mail]

http://r-gis.net

References

Naimi. B. et al. (under review) ELSA: An Entropy-based Local indicators of Spatial Association, Geographical Analysis;

Examples

## Not run: 
file <- system.file('external/dem_example.grd',package='elsa')

r <- raster(file)

plot(r,main='a continuous raster map')

et <- elsa.test(r,d=2000,n=99)

plot(et)


## End(Not run)

elsa documentation built on May 2, 2019, 4:49 p.m.