Basketball Statistics Blog

eBA Encyclopedia Statistics Terminology: Heat Map

A heat map is a graphical representation of data where the values taken by a variable in a two-dimensional map are represented as colors. A very similar presentation form is a tree map. The term is also used to mean its thematic application as a choropleth map.

There are several different kinds of heat map:

• Web heat maps have been used for displaying areas of a Web page most frequently scanned by visitors.
• Biology heat maps are typically used in molecular biology to represent the level of expression of many genes across a number of comparable samples (e.g. cells in different states, samples from different patients) as they are obtained from DNA microarrays.
• The tree map is a 2D hierarchical partitioning of data that visually resembles a heat map.
• A mosaic plot is a tiled heat map for representing a two-way or higher-way table of data. As with treemaps, the rectangular regions in a mosaic plot are hierarchically organized. The means that the regions are rectangles instead of squares. Friendly (1994) surveys the history and usage of this graph.

Image: Information Aesthetics

Each NBA Basketball Team Heat Map shows who was coaching the basketball team that year, who were the top offensive players on the team, and by how many possessions each team won or lost over a 5 year period.

The overall goal of the charts is to be able to observe how time, coaches and players create point spread trends. Win percentage paints a narrow picture of how key personnel react to being put into different game situations. Year-over-year trends may help people see why their team is gaining or losing ground to the competition.

Each color is a point range that the team won or lost by in that year. Green to red bars are wins, while blues are losses. The lower area provides team information for each year. The right bar shows the average share of games won ad lost by each 3-point range over the last 5 year in the NBA.

One of the discovered insights is how certain teams and coaches are more likely to win by 3 or fewer points than they lose by the same margin.

Read More more details about this definition and another statistical terms at our new Statistics Terminology Glossary.

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