Added ZCTA geography

For analysis by 5-digit ZIP Code

Author: nmpeterson

DESCRIPTION

@@ -1,6 +1,6 @@
 Package: cmapgeo
 Title: R-Friendly Geodata for the Chicago Region
-Version: 0.1.0
+Version: 0.1.1
 Authors@R: c(
     person("Noel", "Peterson",
            role = c("aut", "cre"),

R/data.R

@@ -203,6 +203,67 @@
 "puma_sf"
 
 
+#' Census ZIP Code Tabulation Areas (ZCTAs)
+#'
+#' The Census ZCTAs covering the 7-county Chicago Metropolitan Agency for
+#' Planning (CMAP) region. From the US Census Bureau's TIGER/Line shapefiles,
+#' 2019 vintage.
+#'
+#' Census Bureau description:
+#'
+#' *ZIP Code Tabulation Areas (ZCTAs) are approximate area representations of
+#' U.S. Postal Service (USPS) five-digit ZIP Code service areas that the Census
+#' Bureau creates using whole blocks to present statistical data from censuses
+#' and surveys. The Census Bureau defines ZCTAs by allocating each block that
+#' contains addresses to a single ZCTA, usually to the ZCTA that reflects the
+#' most frequently occurring ZIP Code for the addresses within that tabulation
+#' block. Blocks that do not contain addresses but are completely surrounded by
+#' a single ZCTA (enclaves) are assigned to the surrounding ZCTA; those
+#' surrounded by multiple ZCTAs will be added to a single ZCTA based on limited
+#' buffering performed between multiple ZCTAs. The Census Bureau identifies
+#' five-digit ZCTAs using a five-character numeric code that represents the most
+#' frequently occurring USPS ZIP Code within that ZCTA, and this code may
+#' contain leading zeros.*
+#'
+#' *There are significant changes to the 2010 ZCTA delineation from that used in
+#' 2000. Coverage was extended to include the Island Areas for 2010 so that the
+#' United States, Puerto Rico, and the Island Areas have ZCTAs. Unlike 2000,
+#' when areas that could not be assigned to a ZCTA were given a generic code
+#' ending in "XX" (land area) or "HH" (water area), for 2010 there is no
+#' universal coverage by ZCTAs, and only legitimate five-digit areas are
+#' defined. The 2010 ZCTAs will better represent the actual Zip Code service
+#' areas because the Census Bureau initiated a process before creation of 2010
+#' blocks to add block boundaries that split polygons with large numbers of
+#' addresses using different ZIP Codes.*
+#'
+#' *Data users should not use ZCTAs to identify the official USPS ZIP Code for
+#' mail delivery. The USPS makes periodic changes to ZIP Codes to support more
+#' efficient mail delivery. The ZCTAs process used primarily residential
+#' addresses and was biased towards ZIP Codes used for city-style mail delivery,
+#' thus there may be ZIP Codes that are primarily nonresidential or boxes only
+#' that may not have a corresponding ZCTA.*
+#'
+#' @format
+#' A multipolygon `sf` object with `r nrow(zcta_sf)` rows and `r ncol(zcta_sf)`
+#' variables:
+#' \describe{
+#'   \item{geoid_zcta}{Unique 5-digit ZCTA ID, corresponding to a 5-digit USPS
+#'   ZIP Code. Character.}
+#'   \item{sqmi}{Area in square miles. Double.}
+#'   \item{geometry}{Feature geometry. `sf` multipolygon.}
+#' }
+#'
+#' @source
+#' US Census Bureau
+#' [TIGER/Line](https://www.census.gov/geographies/mapping-files/time-series/geo/tiger-line-file.html)
+#'
+#' @examples
+#' # Display the ZCTAs with ggplot2
+#' library(ggplot2)
+#' ggplot(zcta_sf) + geom_sf(lwd = 0.1) + theme_void()
+"zcta_sf"
+
+
 #' Illinois State Senate Districts
 #'
 #' The Illinois General Assembly Senate Districts. From the US Census Bureau's

data-raw/load_census_api.R

@@ -148,6 +148,15 @@ ilga_senate_sf <- tigris::state_legislative_districts(state = STATE, house = "up
   select(dist_num, dist_name, cmap, sqmi) %>%
   arrange(dist_num)
 
+# Process ZIP Code Tabulation Areas (ZCTAs)
+zcta_sf <- tigris::zctas(starts_with = "6") %>%
+  sf::st_transform(cmap_crs) %>%
+  filter(intersects_cmap(.)) %>%  # Restrict to CMAP region
+  rename(geoid_zcta = GEOID10) %>%
+  mutate(sqmi = unclass(sf::st_area(geometry) / sqft_per_sqmi)) %>%
+  select(geoid_zcta, sqmi) %>%
+  arrange(geoid_zcta)
+
 # Process IDOT regions
 county_district = c(
   `17031`="D1", `17089`="D1", `17197`="D1", `17043`="D1", `17097`="D1", `17111`="D1",
@@ -184,4 +193,5 @@ usethis::use_data(puma_sf, overwrite = TRUE)
 usethis::use_data(congress_sf, overwrite = TRUE)
 usethis::use_data(ilga_house_sf, overwrite = TRUE)
 usethis::use_data(ilga_senate_sf, overwrite = TRUE)
+usethis::use_data(zcta_sf, overwrite = TRUE)
 usethis::use_data(idot_sf, overwrite = TRUE)