SP: A function to compute the spatial proximity index (SP)

Description Usage Arguments Value References See Also Examples

View source: R/SegFunctions.R

Description

The spatial proximity index, SP, compares the clustering level (mean proximity) of a group compared to another group. 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

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SP(x, d = NULL, fdist = 'e', distin = 'm',  distout = 'm', diagval = '0', 
itype = 'multi', 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

fdist

- the method used for distance interaction matrix: e' for inverse exponential function (by default) and 'l' for linear.

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)

itype

- a character string defining the index type: itype = 'multi' (by default) for the multi-group index (White, 1986), itype = 'between' for the between groups version (White, 1983), or itype = 'one' for the one-group version (Apparicio et al, 2008)

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

spatial proximity index value(s)

References

White M. J. (1983) The Measurement of Spatial Segregation. American Journal of Sociology, 88, p. 1008-1019.

White, M. J. (1986) Segregation and Diversity Measures in Population DistributionE. Population Index 52(2): 198-221.

Apparicio, P., V. Petkevitch and M. Charron (2008): Segregation Analyzer: A C#.Net application for calculating residential segregation indices, Cybergeo: European Journal of Geography, 414, 1-27.

See Also

Proximity measures: Pxx, Pxy, Poo

Clustering Indices: ACL, RCL

Examples

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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'

SP(x, spatobj = segdata)

SP(x, folder = foldername, shape = shapename, fdist = 'l', itype = 'between') 

SP(x, spatobj = segdata, diagval ='a', itype = 'one')

SP(x, d = dist, fdist = 'e')

OasisR documentation built on Aug. 30, 2017, 5:06 p.m.