Two US county maps that are the basis for almost every choropleth map of the US you see: Population Density, and Percent Black.
US County Maps in R
http://kieranhealy.org/blog/archives/2015/06/12/americas-ur-choropleths/
Two US county maps that are the basis for almost every choropleth map of the US you see: Population Density, and Percent Black.
US County Maps in R
http://kieranhealy.org/blog/archives/2015/06/12/americas-ur-choropleths/