Make a Shot-Density Heatmap with hexbin

Try to plot 25,000 shots as a scatter and you get a black blob — every interesting pattern buried under overlapping dots. The fix is hexbin: tile the court into hexagons and color each one by what's inside it. It's a histogram in two dimensions, and it's the foundation of every shot chart, heat map, and spatial-density plot you've ever seen. By the end you'll have two maps — where shots come from, and where they actually go in.

This builds on Your First Sports Data Visualization and Binning Data with pd.cut (hexbin is binning in 2D). The data is the bundled nba_league_shots.csv (25,000 real NBA shot locations), so it runs offline.

1. Load the shots and look at the coordinates

   Each row is one shot with an LOC_X (left-right, in feet from center) and LOC_Y (distance up the court). We keep the front-court half, where essentially all shots happen.

   import pandas as pd
   
   shots = pd.read_csv("nba_league_shots.csv")
   shots = shots[(shots["LOC_Y"] >= 0) & (shots["LOC_Y"] <= 40)]
   print(len(shots), "shots")
   print(shots[["LOC_X", "LOC_Y", "SHOT_MADE"]].head())

   What's in the file

   Shots loaded: 24930
   X (left-right) range: -25 to 25 feet
   Y (up the court) range: 1 to 40 feet
   Overall make rate: 47.3%

   Coordinates plus a made/missed flag are all hexbin needs. The hoop sits near (0, 0); positive LOC_Y moves out toward half-court.

2. The density map: where shots come from

   One call does it. hexbin takes the x and y arrays, splits the plane into a grid of hexagons (gridsize controls how many), and colors each by the count of points inside. mincnt=1 hides empty hexes so the court background stays clean.

   import matplotlib.pyplot as plt
   
   fig, ax = plt.subplots(figsize=(7.5, 7))
   hb = ax.hexbin(shots["LOC_X"], shots["LOC_Y"], gridsize=30,
                  cmap="inferno", mincnt=1)
   fig.colorbar(hb, ax=ax, label="shots in hex")
   ax.set_aspect("equal")          # don't distort the court!
   fig.savefig("shot_density.png", dpi=144, bbox_inches="tight")

   

   The shape of the modern NBA appears instantly: a blazing cluster right at the rim, a bright ring along the three-point arc, and a sparse, dim mid-range between them. That set_aspect("equal") line matters — without it the court stretches and the hexagons turn into ovals, distorting every distance.

3. The efficiency map: the real payoff

   Density shows where teams shoot; the better question is where they score. hexbin can color each hex by any statistic, not just a count: pass C= a value per point and reduce_C_function= how to aggregate it. Feed it the made/missed flag with np.mean and each hex shows its make rate. We require at least 20 shots per hex (mincnt=20) so a lucky 1-for-1 hex doesn't paint a fake 100%.

   import numpy as np
   
   fig, ax = plt.subplots(figsize=(7.5, 7))
   hb = ax.hexbin(shots["LOC_X"], shots["LOC_Y"],
                  C=shots["SHOT_MADE"].astype(float),   # the value to aggregate
                  reduce_C_function=np.mean,             # mean of made(1)/missed(0) = make rate
                  gridsize=30, cmap="RdYlGn", mincnt=20)
   fig.colorbar(hb, ax=ax, label="make rate")
   ax.set_aspect("equal")
   fig.savefig("shot_efficiency.png", dpi=144, bbox_inches="tight")

   

   That C / reduce_C_function pair is the trick worth remembering: swap in any column and any function and the same map shows average shot distance, average shot value, anything per location. It turns a density plot into an analytics tool.

4. Read the map in numbers

   A chart should always be backed by the figures. Group by the zone label and check the make rates the colors are showing.

   z = (shots.groupby("BASIC_ZONE")
        .agg(shots=("SHOT_MADE", "size"), make_rate=("SHOT_MADE", "mean"))
        .sort_values("shots", ascending=False))
   print(z)

   Make rate by zone

   Shots and make rate by zone:
                          shots  make_rate
   BASIC_ZONE                             
   Restricted Area         7379       65.8
   Above the Break 3       7238       36.1
   In The Paint (Non-RA)   4971       44.2
   Mid-Range               2779       40.9
   Left Corner 3           1310       38.9
   Right Corner 3          1253       38.2
   
   The restricted area is bright green (high make rate); the long
   mid-range is the cold yellow band the modern NBA has abandoned.

   The restricted area converts around 66% and the long mid-range around 41% — the exact gap that pushed the league toward layups and threes. The map didn't just look nice; it pointed straight at the most important strategic shift in modern basketball.

Troubleshooting