Chapter 9. Dynamic graphs: how to show data over time


This chapter covers

  • How to present data when it has a date/time element
  • What to do with data that changes over time
  • How to deal with graph elements that contain durations

So far, one of the major themes of this book is that although static graph visualizations are good, interactivity is far better. Allowing for interaction with graph visualizations offers an additional element that significantly enhances the user experience and the ease by which viewers can gain valuable information about the data contained in the graph. In a sense, those interactive graph visualizations are dynamic in that the user can control what they’re seeing by laying out the data differently or applying filters. That’s not what I talk about in this chapter. Here, when I say dynamic graphs, I mean graphs where the data itself is changing over time, such as when you’re looking at financial transactions (cash transfers between bank accounts, for example) or census information (such as migration patterns of human movements between countries). How do you show graphs over time? You need to figure out exactly what that means, and there are two scenarios where you might want to do this:

  • Visualizing how you changed your graph over time. (What new data did you add to your graph, and when did you add it?)
  • Visualizing graph data that has some sort of date/time property. (How do you illustrate dates and times in your data?)

9.1. How do graphs change over time?

9.2. How to visualize changes over time

9.3. Implementing dynamic graphs

9.4. Summary