Calculates the spatial Gini index for a given numeric vector and neighbor list. Based on the formula provided Rey and Smith (2013).

## Arguments

- x
a numeric vector without missing values

- nb
a neighbor list, for example created with

`st_contiguity()`

## Value

A data frame with columns:

`G`

: the Gini index`NBG`

: the neighbor composition of the Gini coefficient`NG`

: the non-neighbor composition of the Gini coefficient`SG`

: the Spatial Gini which is equal to \(NG * \frac{1}{G}\)

## Details

The Gini index is a global measure of inequality based on the Lorenz curve. It ranges between 0 and 1 where 0 is perfect equality and 1 is perfect inequality.

The spatial Gini index decomposes the Gini coefficient based on spatial neighbors.

## Examples

```
nb <- st_contiguity(guerry)
x <- guerry$wealth
spatial_gini(x, nb)
#> G NG NBG SG
#> 1 0.3306568 0.3164337 0.0142231 0.9569853
```