Reading a shot chart: zones, dots and colour scales
Data visuals
How to interpret the six standard shooting zones, what a red hexagon actually means, and why a small chart is mostly noise.
A shot chart is a picture of where a team or a player attempted shots, drawn on a plan view of the half court. Every version you will see is built from the same two ingredients: position on the floor, and whether the shot went in.
The simplest form is the dot chart. One mark per attempt, filled for a make and hollow for a miss, or two colours doing the same job. It is honest, it is readable, and it shows you shape immediately: a guard whose dots cluster in the corners and at the rim is playing a very different role from one whose dots sit in an arc fifteen feet out.
The more common form bins the shots into zones. The standard six are the restricted area under the rim, the rest of the paint, the mid-range, the two corner threes and the above-the-break three. Each zone gets a number of attempts and a shooting percentage. The zones exist because shot value changes sharply at the arc and again at the edge of the paint, so averaging across the whole floor hides the thing you want to know.
Then come the heat maps, usually hexagons. Two variables are encoded at once and this is where people misread them. Hexagon size normally means volume, how many shots were taken from that spot. Hexagon colour normally means efficiency compared to an average, not raw percentage. A small, bright hexagon is a player who has made almost everything from a spot he has barely shot from. It is not a finding, it is three shots.
That is the main caution with any shot chart: sample size. A single game produces perhaps sixty attempts for a whole team, which means five or six per zone and nothing worth colouring. Charts become informative over dozens of games, and even then a mid-range zone with twenty attempts will swing wildly on a handful of makes.
What a chart does show reliably, even over a short span, is intent. Where a team chooses to shoot from is a decision it makes every possession, and decisions stabilise long before percentages do. A chart with a hole in the mid-range and heavy clusters at the rim and behind the arc is telling you about a system. A chart with an even spread across the floor is telling you about a different one, usually an older one, and about a team that is comfortable taking the shot the defence offers rather than hunting a particular kind.