DIWong: A function to compute Wongs's dissimilarity index

Description

Wong's dissimilarity index is a development of DIDuncan's which takes into account the interactions between spatial units(common boundaries and perimeter/area ratios). 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

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

Value

a matrix containing Wong's dissimilarity index values

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 borders of spatial units, and 'all' to use entire borders, including to the exterior of the area
variant: - a character variable that allows to choose the index version: variant = 's' for the dissimilarity index adjusted for contiguous spatial units boundary lengths and perimeter/area ratio (by default) and variant = 'w' for the version without perimeter/area ratio
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. (1993) Spatial Indices of Segregation. Urban Studies, 30 (3), pp. 559-572.

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'

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

DIWong(x, spatobj = segdata, variant = 'w') 

DIWong(x, folder = foldername, shape = shapename, ptype ='all')