Humans crave context when evaluating data, so it’s important to provide that context when it’s available. In the previous chapter, we saw how timelines can provide one frame of reference; now we’ll examine another equally important context: place. If a data set includes geographic coordinates or has values that correspond to different geographic regions, you can provide geographic context using a map-based visualization. The examples in this chapter consider two types of map-based visualizations.
In the first two examples, we want to show how data varies by region. The resulting visualizations, known as choropleth maps, use color to highlight different characteristics of the different regions. For the next two examples the visualization data doesn’t itself vary by region directly, but the data does have a geographic component. By showing the data on a map, we can help our users understand it.
More specifically, we’ll see
- How to use special map fonts to create maps with minimal JavaScript.
- How to manipulate Scalable Vector Graphic (svg) image maps with JavaScript.
- How to use a simple mapping library to add maps to web pages.
- How to integrate a full-featured map library into a visualization.