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63 lines
2.4 KiB
63 lines
2.4 KiB
#' Retrieve a U.S. county composite map, optionally with a projection, as a simplefeature
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#'
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#' The \code{proj} parameter is intende to simplify usage for those using base
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#' plotting. If anything but \code{longlat} is specified the composite map
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#' will be pre-projected to those
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#'
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#' This is what's in the object looks like:
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#'
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#' \preformatted{
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#' Observations: 3,143
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#' Variables: 9
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#' $ fips <fctr> 01001, 01009, 01017, 01021, 01033, 01045, 01051, 01065, 01079, 0...
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#' $ state_fips <fctr> 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 05, 05, 06, ...
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#' $ county_fips <fctr> 001, 009, 017, 021, 033, 045, 051, 065, 079, 083, 099, 107, 121,...
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#' $ name <fctr> Autauga, Blount, Chambers, Chilton, Colbert, Dale, Elmore, Hale,...
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#' $ lsad <fctr> County, County, County, County, County, County, County, County, ...
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#' $ census_area <dbl> 594.436, 644.776, 596.531, 692.854, 592.619, 561.150, 618.485, 64...
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#' $ state <fctr> Alabama, Alabama, Alabama, Alabama, Alabama, Alabama, Alabama, A...
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#' $ iso_3166_2 <fctr> AL, AL, AL, AL, AL, AL, AL, AL, AL, AL, AL, AL, AL, AR, AR, CA, ...
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#' $ geometry <simple_feature> MULTIPOLYGON(((-86.496774 3..., MULTIPOLYGON(((-86.577...#' }
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#'
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#' A reference GeoJSON file isprovided in the following location (i.e. you can use
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#' it in any mapping program):
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#'
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#' \preformatted{
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#' system.file("extdata/composite_us_counties.geojson.gz", package="albersusa")
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#' }
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#'
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#' @param proj if anything but \code{longlat} is specified, the shapefile will
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#' be pre-projected before being returned
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#' @export
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#' @examples
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#' library(sf)
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#'
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#' plot(counties_sf()) # these take a while to render
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#' plot(counties_sf("laea"))
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counties_sf <- function(proj=c("longlat", "laea", "lcc", "eqdc", "aeqd")) {
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# us <- readOGR(system.file("extdata/composite_us_counties.geojson", package="albersusa"),
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# "OGRGeoJSON",
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# stringsAsFactors=FALSE,
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# verbose=FALSE)
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cty <- readRDS(system.file("extdata/counties_sf.rda", package="albersusa"))
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# saveRDS(cty, "inst/extdata/counties_sf.rda", version = 2)
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proj <- match.arg(proj, c("longlat", "laea", "lcc", "eqdc", "aeqd"))
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if (proj != "longlat") {
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proj <- switch(proj,
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laea=us_laea_proj,
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lcc=us_lcc_proj,
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eqdc=us_eqdc_proj,
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aeqd=us_aeqd_proj)
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cty <- sf::st_transform(cty, proj)
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}
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cty
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}
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