R/ll_get_us.R

In giocomai/latlon2map: Facilitates matching lat/lon data with administrative units and other geographic shapes

#' Get US counties
#'
#' Source: https://www.census.gov/geographies/mapping-files/time-series/geo/carto-boundary-file.html
#'
#' @param level Defaults to "county". Available options are: "cd116" (for congressional districts of the 116th Congress)
#' @param resolution Defaults to "500k", max available resolution. Available options are: "5m" and "20m"
#' @param year Defaults to 2018
#'
#' @return
#' @export
#'
#' @examples
#' ll_get_nuts_us(level = "county", resolution = "500k", year = 2018)
ll_get_nuts_us <- function(level = "county",
                           resolution = "500k",
                           year = 2018) {
  usethis::ui_info("Source: https://www.census.gov/geographies/mapping-files/time-series/geo/carto-boundary-file.html")
  ll_create_folders(
    geo = "us",
    level = level,
    resolution = resolution,
    year = year
  )

  rds_file <- ll_find_file(
    geo = "us",
    level = level,
    resolution = resolution,
    year = year,
    name = "abl",
    file_type = "rds"
  )

  if (fs::file_exists(rds_file)) {
    return(readRDS(file = rds_file))
  }

  shp_folder <- ll_find_file(
    geo = "us",
    level = level,
    resolution = resolution,
    year = year,
    name = "abl",
    file_type = "shp"
  )

  zip_file <- ll_find_file(
    geo = "us",
    level = level,
    resolution = resolution,
    year = year,
    name = "abl",
    file_type = "zip"
  )
  source_url <- paste0("https://www2.census.gov/geo/tiger/GENZ2018/shp/cb_", year, "_us_", level, "_", resolution, ".zip")

  if (fs::file_exists(zip_file) == FALSE) {
    download.file(
      url = source_url,
      destfile = zip_file
    )
  }
  unzip(
    zipfile = zip_file,
    exdir = shp_folder
  )
  sf <- sf::read_sf(shp_folder)
  saveRDS(
    object = sf,
    file = rds_file
  )
  return(sf)
}