OasisR (version 2.0.1)

Pxx: A function to compute the mean proximity between members of a group (Pxx)

Description

Mean proximity, Pxx, computes the mean distance between the members of a group. The distance matrix can be expressed as a linear or as an inverse exponential function of the distance between spatial units centroids.The function can be used in two ways: to providea a distance matrix or a external geographic information source (spatial object or shape file).

Usage

Pxx(x, d = NULL, fdist = 'e', distin = 'm',  distout = 'm', diagval = '0', 
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 population group, within spatial units. The number of columns should be greater than 1 (at least 2 population groups are required). You should not include a column with total population in each unit, 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 units area) (White, 1983)

spatobj

- a spatial object (SpatialPolygonsDataFrame) containing geographic information

folder

- a character vector with the folder (directory) name indicating where the shapefile with the geographic information is located.

shape

- a character vector with the name of the shapefile (without the .shp extension) which contains the geographic information

Value

a numeric vector containing Pxx index value for each population group

References

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

See Also

Proximity measures: Pxy, Poo, SP

Clustering Indices: ACL, RCL

Examples

# NOT RUN {
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'

Pxx(x, spatobj = segdata)

Pxx(x, folder = foldername, shape = shapename, fdist = 'l') 

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

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

# }