• Overview
• Parameters
  • data_subfolder
  • county_fips_codes
  • state_fips_codes
  • image_dimensions
  • image_lat and image_lon
  • road_thickness

This script generates a road map of the San Francisco Bay Area using only ggplot2, magick, and freely available data provided by the US Census Bureau’s TIGER/Line geodatabases. It includes the coastline, all bodies of water, and all paved roads, with the roads colored as they pass through municipal city boundaries.

Because everything here is generated programmatically, it’s all entirely adjustable. I’ve created a set of user-adjustable parameters in a section near the top of the script for ease of use.

This script automatically fetches all necessary data from the Census Bureau and saves and unpacks everything in a subfolder. By default, this is a subfolder in the working directory named “data”, but this can be changed if needed.

Data for area hydrography and road paths are organized by TIGER/Line in separate files for each county. This script can be used to plot different areas of the country by supplying a different vector of files to download. A list of county FIPS codes in the United States can be found here.

Unlike the water and road data, city boundary data is organized by state. A list of state FIPS codes can be found here.

By default, this script generates a 9600 by 12000 pixel image, only because that results in a 24 by 30 inch image at 400dpi. This can be adjusted to any dimension size, but note that if this is dramatically increased, it can result in pretty lengthy plot times.

These two parameters control the latitude and longitude of the plotted geographic area.

This parameter is a numeric vector of length 2 because it directly feeds into the ggplot2::scale_size() plotting function, telling ggplot2 how thick to plot the thinnest and thickest styles of roads on the map, respectively. All intermediate road styles will be scaled to match the range given here. If the image_dimensions parameter is changed, this may have to be adjusted as well.