Annotating a map
Our final examples of working with maps will demonstrate making annotations to a map. The first two will demonstrate placing labels and markers on a map, and the third will demonstrate the use of gradient colors to color regions all the way down to a state level.
All of these techniques would normally involve some fairly complex math if we had to do it on our own, but thankfully, D3.js again comes to help us solve this with just a few statements.
Labelling states using centroids
The maps of the United States we've created up to this point feel a little lacking in content, as they have not had the names of the states placed over their geometries. It would be very helpful to many reading a map to have the names visible. The example ...