Compute the Individual Species Area Relationship ( ISAR ) or Local Species Richness, for a given multitype point pattern.
isarF(X, r = NULL, target = NULL, v2 = FALSE, v3 = FALSE,
v4 = FALSE, ...)isar.index(X, r = 4, ntype = "knn", ...)
Multitype point pattern of class ppp (see package 'spatstat')
Vector of sizes for neighbourhoods, e.g. geometric graph with
different ranges.
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)
Further parameters for the function segregationFun.
Sets the n'hood type to knn by default in isar.index.
isar.index: Shortcut for 4-nearest neighbour value.
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.
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.