Make Patterns Pop Out of Heatmaps with Seriation

One of the easiest ways to start visualizing data is to turn a table into a heatmap: every cell gets a colour, the higher the number the brighter the colour. Unfortunately, this is often a fairly unrewarding exercise, yielding graphics that look like plaid or tartan fabric. Part of the problem is that the rows and columns of a dataset often have no natural ordering, such as time, and are instead shown in alphabetical order, or else the dataset is sorted by one of the rows or columns, rather than in an order which makes patterns pop out visually. My goal in this article is to clearly demonstrate this problem and show that there exist neat solutions to this problem using a set of techniques collectively called seriation. I'll do this by automatically reordering the rows and columns in the following noisy-looking heatmap to make the underlying pattern very clear.