We created datasets that contain the data we need to visualize average pay and employment by county and state. In this recipe, we will visualize the geographical distribution of pay by shading the appropriate areas of the map with a color that maps to a particular value or range of values. This is commonly referred to as a chloropleth map; this visualization type has become increasingly popular over the last few years as it has become much simpler to make such maps, especially online. Other geographic visualizations will overlay a marker or some other shape to denote data; there is no need to fill specific shapes with geographically meaningful boundaries.
After the last recipe, you should be ready to use the datasets we created to visualize geographical distributions. We will use the ggplot2 package to generate our visualizations. We will also use the RColorBrewer package, which provides "palettes" of colors that are visually appealing...