# Pxx: A function to compute the mean proximity between members of a... In OasisR: Outright Tool for the Analysis of Spatial Inequalities and Segregation

## 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 unit centroids.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

 ```1 2``` ```Pxx(x, d = NULL, fdist = 'e', 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 `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) `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 Pxx index value for each group

## References

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

Proximity measures: `Pxy`, `Poo`, `SP`
Clustering Indices: `ACL`, `RCL`
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14``` ```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') ```