Choropleth maps use shading to represent quantities and are common in the press. I gave them a go in R, using the rvest package to scrape the results of the 2020 Russian constitutional referendum and the raster package piped through tidyverse tools to map them.
The code is on my GitHub repo.
Some of the fun I encountered along the way (details in the repo):
- The CRAN version of raster didn’t work, but the latest on GitHub was fine and it’s easy to install this directly from R.
- The Russian regions names in the raster map of Russia didn’t always match those on the Wikipedia article. I tried fuzzy matching by edit distance, which did a pretty good job but I still had to match some manually (e.g., “Sakha” and “Yakutia” are different names for the same place and a long edit distance from each other). I suspect it would have been easier just to sort both lists alphabetically and match manually from the start!
- This warning is a worry: “support for gpclib will be withdrawn from maptools at the next major release” – I hope something comes along to replace it.
- Lots of the examples of maps online are for the US and one basic problem is what projection to use. The mapproj package is fab for this.