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Compute Rural Access Index (RAI)

Source: R/l4h_rural_access_index.R
l4h_rural_access_index.Rd

Calculates the Rural Access Index (RAI) for a given region using datasets from the GEE Community Catalog. The RAI represents the proportion of the rural population living within 2 km of an all-season road, aligning with SDG indicator 9.1.1.

[Stable]

Usage

l4h_rural_access_index(
  region,
  weighted = FALSE,
  fun = NULL,
  sf = FALSE,
  quiet = FALSE,
  force = FALSE,
  ...
)

Arguments

region

A spatial object defining the region of interest. Can be an sf, sfc object, or a SpatVector (from the terra package).

weighted

Logical. If TRUE, computes a population-weighted RAI (i.e., rural population with access divided by total rural population). If FALSE, computes an area-based RAI (i.e., total pixel area with access divided by total rural area). Default is FALSE.

fun

Character. Summary function to apply to the population raster when weighted = TRUE. Common values include "mean", "sum", etc. Ignored when weighted = FALSE. Default is "mean".

sf

Logical. If TRUE, returns the result as an sf object. If FALSE, returns an Earth Engine object. Default is FALSE.

quiet

Logical. If TRUE, suppress the progress bar (default FALSE).

force

Logical. If TRUE, skips the representativity check and forces the extraction. Default is FALSE.

...

arguments of ee_extract of rgee packages.

Value

A spatial object containing the computed RAI value for the region in an sf or tibble object.

Details

This function uses the following datasets from the GEE Community Catalog:

  • projects/sat-io/open-datasets/RAI/ruralpopaccess – raster of rural population with access to all-season roads

  • projects/sat-io/open-datasets/RAI/inaccessibilityindex – binary raster indicating access areas (1 = access, 0 = no access)

When weighted = TRUE, the RAI is calculated as the sum (or chosen summary via fun) of the accessible rural population divided by the total rural population within the specified region.

When weighted = FALSE, the RAI is calculated as the ratio of pixel areas: the total area (in km²) with access divided by the total rural area.

The fun parameter only applies when weighted = TRUE. It will be ignored otherwise.

References

GEE Community Catalog: https://gee-community-catalog.org/projects/rai

Frontiers in Remote Sensing (2024): doi:10.3389/frsen.2024.1375476

Examples

if (FALSE) { # \dontrun{
library(land4health)
ee_Initialize()
# Population-weighted RAI
l4h_rural_access_index(region, weighted = TRUE, fun = "sum", sf = TRUE)

# Area-based RAI
l4h_rural_access_index(region, weighted = FALSE, sf = TRUE)
} # }