ISWong: A function to compute Wong's segregation index

Description

Wong's segregation index is a development of ISDuncan's which takes into account the interactions between spatial units (common boundaries and perimeter/area ratio). The function can be used in two ways: to provide spatial data ( boundaries matrix, a perimeter vector and an area vector) or a external geographic information source (spatial object or shape file).

Usage

ISWong(x, b = NULL,  a = NULL, p = NULL, ptype = 'int', variant = 's', 
spatobj = NULL, folder = NULL, shape = NULL)

Value

a numeric vector containing the Wong's segregation index value for each group

Arguments

x: - an object of class matrix (or which can be coerced to that class), where each column represents the distribution of a group within spatial units. The number of columns should be greater than 1 (at least 2 groups are required). You should not include a column with total totals because this will be interpreted as a group
b: - a common boundaries matrix where each element Bij equals the shared boundary of i-th and j-th spatial units.
a: - a numeric vector containing spatial unit areas
p: - a numeric vector containing spatial units perimeters.
ptype: - a string variable giving two options for perimeter calculation when a spatial object or shapefile is provided: 'int' to use only interior boundaries of spatial units, and 'all' to use entire boundaries, including the boundaries to the exterior
variant: - a character variable that allows to choose the index version: variant = 's' for the index adjusted for contiguous spatial/organizational units boundary lengths and perimeter/area ratio (by default) and variant = 'w' for the version based only on shared boundaries length
spatobj: - a spatial object (SpatialPolygonsDataFrame) with geographic information
folder: - a character vector with the folder (directory) name indicating where the shapefile is located on the drive
shape: - a character vector with the name of the shapefile (without the .shp extension).

References

Wong D. W. S. (1998) Measuring multiethnic spatial segregation. Urban Geography, 19 (1), pp. 77-87.

Examples

Run this code

x <- segdata@data[ ,1:2]
bound <- boundaries(segdata)
per <- perimeter(segdata)
ar <- area(segdata)
foldername <- system.file('extdata', package = 'OasisR')
shapename <- 'segdata'

ISWong(x, b = bound, p = per, a = ar) 

ISWong(x, spatobj = segdata, variant = 's', ptype = 'int')

ISWong(x, folder = foldername, shape = shapename, variant = 'w')