isarF: Individual Species Area Relationship

Description

Compute the Individual Species Area Relationship ( ISAR ) or Local Species Richness, for a given multitype point pattern.

Usage

isarF(X, r=NULL, target=NULL, v2=FALSE, v3=FALSE, v4=FALSE, ... )
isar.index(X, r=4, ntype="knn", ...)

Arguments

Multitype point pattern of class ppp (see package 'spatstat')

Vector of sizes for neighbourhoods, e.g. geometric graph with different ranges.

target

Default NULL. Calculate only for target type. If NULL computes for each type + mean over all types.

Logical. Estimate species-to-neighbours-ratio instead of just total number of species.

Logical. Instead of summing number 1 for each species present, sum the average X$mass of each species present.

Logical. Estimate ISAR using empty space probabilities instead of direct counts (equals the normal version in all my tests)

ntype

Sets the n'hood type to knn by default in isar.index.

...

Further parameters for the function segregationFun.

Value

Returns an fv-object, see spatstat for more information.

Details

Extension of ISAR-function introduced in WGGH07. In effect calculates the expected amount of different types present in the neighbourhood of a point in the pattern.

The function isarF is the calculation function for different neighbourhoods. Uses function segregationFun.

The function isar.index is a shortcut to get a single value for the pattern. Uses 4-nn graph by default.

References

Rajala, Illian: A family of spatial biodiversity measures based on graphs, Env. Ecol. Stat. 2012

Wiegand, Gunatilleke, Gunatilleke, Huth: How individual species structure diversity in tropical forests. PNAS, nov 16, 2007.