R/counties.r

In hrbrmstr/albersusa: Tools, Shapefiles & Data to Work with an 'AlbersUSA' Composite Projection

#' Retrieve a U.S. county composite map, optionally with a projection
#'
#' The \code{proj} parameter is intende to simplify usage for those using base
#' plotting. If anything but \code{longlat} is specified the composite map
#' will be pre-projected to those
#'
#' This is what's in the SPDF \code{@data} slot:
#'
#' \preformatted{
#' Observations: 3,143
#' Variables: 9
#' $ fips        (chr) "01001", "01009", "01017", "01021", "01033", "01045", "01051",...
#' $ state_fips  (chr) "01", "01", "01", "01", "01", "01", "01", "01", "01", "01", "0...
#' $ county_fips (chr) "001", "009", "017", "021", "033", "045", "051", "065", "079",...
#' $ name        (chr) "Autauga", "Blount", "Chambers", "Chilton", "Colbert", "Dale",...
#' $ lsad        (chr) "County", "County", "County", "County", "County", "County", "C...
#' $ census_area (dbl) 594.436, 644.776, 596.531, 692.854, 592.619, 561.150, 618.485,...
#' $ state       (chr) "Alabama", "Alabama", "Alabama", "Alabama", "Alabama", "Alabam...
#' $ iso_3166_2  (chr) "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "AL", "A...
#' $ population  (dbl) 54590, 57466, 34228, 43611, 54451, 50129, 79330, 15750, 34148,...
#' }
#'
#' A reference GeoJSON file isprovided in the following location (i.e. you can use
#' it in any mapping program):
#'
#' \preformatted{
#' system.file("extdata/composite_us_counties.geojson.gz", package="albersusa")
#' }
#'
#' @param proj if anything but \code{longlat} is specified, the shapefile will
#'        be pre-projected before being returned
#' @export
#' @examples
#' library(sp)
#'
#' plot(counties_composite())
#' plot(counties_composite("laea"))
counties_composite <- function(proj=c("longlat", "laea", "lcc", "eqdc", "aeqd")) {

  # us <- readOGR(system.file("extdata/composite_us_counties.geojson", package="albersusa"),
  #               "OGRGeoJSON",
  #               stringsAsFactors=FALSE,
  #               verbose=FALSE)

  cty <- readRDS(system.file("extdata/counties.rda", package="albersusa"))
  # saveRDS(cty, "inst/extdata/counties.rda", version = 2)

  proj <- match.arg(proj, c("longlat", "laea", "lcc", "eqdc", "aeqd"))

  if (proj != "longlat") {

    proj <- switch(proj,
                   laea=us_laea_proj,
                   lcc=us_lcc_proj,
                   eqdc=us_eqdc_proj,
                   aeqd=us_aeqd_proj)

    cty <- sp::spTransform(cty, sp::CRS(proj))

  }

  cty

}