Delta: A function to compute Delta index

Description

The Delta index is a specific application of dissimilarity index DIDuncan which simply measures the dissimilarity between the spatial distribution of a population group and the spatial distribution of available area. It can be interpreted as the share of group that would have to move to achieve uniform density over all spatial units. The function can be used in two ways: to provide an area vector or a external geographic information source (spatial object or shape file).

Usage

Delta(x, a = NULL, spatobj = NULL, folder = NULL, shape = NULL)

Arguments

- 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.

- a numeric vector containing the areas of spatial units

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 Delta index value for each population group

References

Duncan O. D., Cuzzoert and Duncan B. (1961) Problems in analyzing areal data. Statistical geography, Glencoe, Illinois: The free press of Glencoe

Examples

Run this code

# NOT RUN {
x <- segdata@data[ ,1:2]
ar <- area(segdata)
foldername <- system.file('extdata', package = 'OasisR')
shapename <- 'segdata'

Delta(x, a = ar) 

Delta(x, spatobj = segdata)

Delta(x, folder = foldername, shape = shapename) 
# }