Vanilla RAPM decomposition
On court signal + Off court adjustment (GP) + Off court adjustment (DNP) + Team SOS adjustment = RAPM
On court rtg + Teammates + Opponents + Context + Ridge penalty = RAPM
Every player's vanilla RAPM, split by which possessions it came from: four pieces that add up to it exactly. Click a player to see his pieces add up.
The same RAPM, split by who was on the court: five pieces that add up to it exactly. Click a player to see his pieces add up.
On court rtg is where this split starts. Off court rtg is the actual rating shown for comparison; it is not a piece.
- On court rtg
- His on-court rating: points per 100 possessions his team scored minus allowed while he was on the court. Only those possessions: nothing from when he sits. The starting point.
- Off court rtg
- Actual: the same with him off the court, in games he played. Shown for comparison; not a piece.
- Teammates
- Minus the combined RAPM of the four teammates on the court with him, weighted by time together. Strong teammates make it negative: they account for part of the margin.
- Opponents
- The combined RAPM of the five opponents on the court with him, weighted by time. Strong opponents make it positive.
- Context
- Minus what home court, playoffs, garbage time, the score margin and the season predict for his minutes.
- Ridge penalty
- The regression's pull toward zero, which keeps small samples from producing extreme ratings. Negative for good players, and larger the fewer possessions he has.
Each piece is exactly how much his RAPM would move if that group of possessions had come out average for their situation. Context and the ridge penalty are not pieces here: context is taken out of every possession, and the penalty sets how much each possession counts. On court rtg and Off court rtg are the actual ratings, shown for comparison; they are not pieces.
- On court rtg
- Actual: points per 100 possessions his team scored minus allowed with him on the court.
- Off court rtg
- Actual: the same with him off the court, in games he played.
- On court signal
- What his own possessions say about him: his team's results with him on the court, measured against what the situation predicts, before any comparison with his team without him. Not a share of the credit: every possession counts for each of his teammates on the court too, so these add up to far more than his team's margin. The off court adjustments make the comparison.
- Off court adjustment (GP)
- How his team did without him, in games he played. A team that falls apart without him adds to his rating; one that stays good takes away.
- Off court adjustment (DNP)
- The same for his team's games he didn't play (injury, rest or coach's decision), in seasons he was on the team. A season missed entirely can't be placed, because injured players aren't in the box scores, so it counts under Team SOS adjustment.
- Team SOS adjustment
- Games his team wasn't in: his teammates' games for other teams, his opponents' games against everyone else, and his team in seasons he wasn't on it. They move his rating only through how good the players around him look: if his opponents prove strong elsewhere, he gets more credit for beating them.
- RAPM
- Vanilla regularized adjusted plus-minus on points: regular season and playoffs, fit on the chosen span alone, ridge penalty 3,000 per side. Unlike the main ratings, it has no box-score prior.