HIPSTER PM v2.3: Shot Portfolio

Last updated: 2026-08-14

HPM v2.3 retains v2.2's empirical rebound and usage-allocation features, then adds a forward-safe shot-portfolio test. It asks whether a unit's available rim pressure is more useful when it is paired with genuine three-point spacing.

For a target season \(t\), every player trait is drawn from \(t-1\). Rim and three-point attempt rates are shrunk toward their source-season league rate with 300 pseudo-possessions, then standardized within that source-season environment. Players without a source-season shot profile receive the league mean, represented by zero after standardization.

For a unit \(U\), the new signals are

\[ R(U)=\sum_{i\in U}\mathrm{rimPressure}_i, \qquad S(U)=\sum_{i\in U}\mathrm{spacingCapacity}_i, \qquad I(U)=R(U)S(U). \]

The bounded hierarchical P-spline model learns separate clipped response functions for \(R\), \(S\), and \(I\). The interaction is strongly regularized and is an initial low-cost approximation to a full two-dimensional rim-pressure-by-spacing surface. It is retained only if it improves the frozen three-season evaluation.

This is a context test, not a claim that rim attempts or threes mechanically cause a lineup outcome. Player shooting and finishing quality remain available to the RAPM prior; these features describe how shot-location capacity combines within a five-player unit.

Run

uv run nba-train-hpm-v23 --through-season 2025-26

The run writes its recursive state and target-season outputs under artifacts/models/forward_hpm_v23_shot_portfolio/.

Frozen Result

On the pooled 2023-24 through 2025-26 frozen regular-season holdouts, v2.3 records a possession RMSE of 1.198025 and a full-game margin RMSE of 14.4288. It does not improve on v2.1 or the value-conditioned aging HPM across the principal regular-season metrics, so the shot-portfolio interaction remains an interpretable experiment rather than a promoted default. Its strongest result is playoff possession MAE, where it leads this comparison at 1.137641. See the Three-Season Frozen Leaderboard for the complete comparison.