DPxx: A function to compute the distance-decay isolation index...

In OasisR: Outright Tool for the Analysis of Spatial Inequalities and Segregation

A function to compute the distance-decay isolation index (DPxx)

Description

The distance decay isolation index, DPxx, is a spatial adaptation of isolation index xPx. The function can be used in two ways: to provide a distance matrix or a external geographic information source (spatial object or shape file).

Usage

DPxx(x, d = NULL, distin = 'm',  distout = 'm', diagval = '0', beta = 1, 
spatobj = NULL, folder = NULL, shape = NULL)

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 population, because this will be interpreted as a group.
d	a matrix of the distances between spatial unit centroids
distin	input metric conversion, based on bink package and includes conversions from 'm', 'km', 'inch', 'ft', 'yd', 'mi', 'naut_mi', etc.
distout	output metric conversion, based on bink package and includes conversions to 'm', 'km', 'inch', 'ft', 'yd', 'mi', 'naut_mi', etc.
diagval	when providing a spatial object or a shape file, the user has the choice of the spatial matrix diagonal definition: diagval = '0' (by default) for an null diagonal and diagval = 'a' to compute the diagonal as 0.6 * square root (spatial/organizational unitsarea) (White, 1983)
beta	distance decay parameter
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).

Value

A numeric vector containing the distance-decay isolation index values for each group

References

Morgan, B. S. (1983) A Distance-Decay Based Interaction Index to Measure Residential Segregation. Area 15(3), pp. 211-217.

See Also

Isolation indices: xPx, Eta2

Interaction indices: xPy, DPxy

Examples

x <- segdata@data[ ,1:2]
ar <- area(segdata)
dist <- distance(segdata)
diag(dist)<-sqrt(ar) * 0.6
foldername <- system.file('extdata', package = 'OasisR')
shapename <- 'segdata'

DPxx(x, d = dist)

DPxx(x, spatobj = segdata, diagval = 'a')

DPxx(x, folder = foldername, shape = shapename, diagval = '0') 

OasisR documentation built on April 3, 2025, 5:58 p.m.