Practical Tableau

Chapter 20. How to Make a Heat Map

Heat maps are a visualization where marks on a chart are represented as colors. As the marks “heat up” due their higher values or density of records, a more intense color is displayed. These colors can be displayed in a matrix/crosstab, which creates a highlight table, but can also be displayed on a geographical map or even a customized image—such as a web page used to show where users are clicking.

Density plots are coming in Tableau version 11, but in the meantime, heat maps are defined somewhat differently in Tableau. This chapter shares how to create a Tableau heat map. If you are interested in creating a traditional heat map using a custom image, see Chapter 35.

To first get more specific about how Tableau defines heat map, let’s take a look at the requirements to draw a heat map under Tableau’s Show Me options:

“For heat maps try 1 or more dimensions and 1 or 2 measures”

This is very close to the requirements for drawing a highlight table with Show Me:

“For highlight tables try 1 or more dimensions and 1 measure”

The key distinction between the two chart types is that with a heat map, you are able to encode the marks by one additional measure. With a highlight table, your only option is to color the marks by one measure. Since you can only color marks by one thing at a time, your encoding is limited to exactly one measure. With a heat map in Tableau, you can color the marks by one measure, but also size the marks by a second measure. Depending ...