Choropleth maps have been extensively used as a medium to represent statistical data. Choropleth maps can be used to represent different data types, such as quantitative, diverging, or qualitative data, using color schemes. The RColorBrewer website provides a great guide to select the color scheme based on the data available to the user. Legends play a very vital role in choropleth maps as we need to state what each color represents in a map.

Choropleth maps can be state level as well as county level. In this recipe, we will plot well-being data on a state level. The data is made available by Gallup (http://www.gallup.com/home.aspx).

Please note that there is more than one way to plot a choropleth map. We can use the basic R plotting function along with the maps package or use ggplot to plot a choropleth map. The benefit of the googleVis package is that it makes the plot interactive and makes it easy to integrate with web pages or blogs.