Tracking the 2008 NBA Playoffs: What the Data Represents

In my post where I detail my data collection goals for the 2008 NBA playoffs, I spell out the sort of data that I’m tracking and adding to the play-by-play. This post will expand on that and describe exactly what you’ll see in the data.

First, a quick reminder of the four types of events I’m adding data to:

1. Shots
2. Turnovers
3. Rebounds
4. Fouls

With that in mind, here is what the fields mean for each event type:

Shots

• assist – I’m not changing much here except that I’m awarding assists even if the shot was missed. Therefore, if the shot was missed, you could say the assist field represents a potential assist. For the curious, I use the 82games definition:
  

  Basically if the player after receiving the pass pauses or dribbles around for a while before taking action it’s not an assist, but otherwise if the player takes the pass and immediately shoots (catch and shoot), drives to the basket, or has a little pump fake type move to throw off the defense and then goes up for the shot (with perhaps one small dribble even) then you’re talking assist.

• opponent – This field is used to track contested shots. I have tried to be as consistent as possible while tracking this data, so let me state my goal for tracking defenders: My goal is to understand the difference between contested and uncontested shots. So the rule of thumb is: If the defender appears to contest the shot then they are tracked as the opponent. Understand that on some shots the opponent tries to contest the shot, but in reality they are too far away and/or come in at a bad angle to get in the shooter’s way. These examples are not counted as contested shots. This field can also be made up of multiple players, in which case the player’s names are separated by the pipe ‘|’ character.
• pick_assist – This is similar to an assist except this player screened an opponent to allow the shooter to obtain spacing, an uncontested shot, or a better matchup. If the screen leads to a shot then that player is credited here, in very much the same way an assist is defined. It is rare, but in the case where two teammates are setting screens, both player’s names are recorded and are separated by the pipe ‘|’ character.
• x and y – These integers represent the shot location in feet. Although I’m not actually tracking this (as that was already done by the great folks that score these games), I have merged the location of the shot into the play-by-play. The translation into the court is simple: If you are standing behind the offensive team’s hoop, then x goes from left to right, and y starts at the baseline behind the hoop all the way up to the baseline behind the opponent’s hoop.

Turnovers

• x and y – These (x,y) coordinates represent the location where possession was gained. These values are translated in the same way as shot location (x,y) coordinates. Note, however, that the team gaining possession is defined as the defensive team. As such, the team losing possession is the offensive team. So keep this in mind when work with these coordinates.

Rebounds

First I want to say that this could be done better (or at least done in a way that will help achieve a specific goal). One of my goals is to try and understand the probability of gaining a rebound when two opponents battle for it. I’m not so sure I’m meeting this goal.

The other goal I have, however, is to understand the likelihood a shot will be rebounded in a specific floor location given the location the shot was taken from. I’m more confident in reaching this goal (or at least understanding it better).

• opponent – This field holds the opponent(s) (seperated by the pipe ‘|’ character) that directly contested the rebounding player. I could go into all sorts of examples, but basically you have to either attempt to get the rebound (say jump in the air and put your arm in the area) or be actively blocked out by the rebounder when the rebound heads in your direction. Opponents just standing around the rebounder are not tracked.
• teammate – This field holds the teammate(s) (seperated by the pipe ‘|’ character) that tried to get the rebound when instead their teammate gained possession. See the definition above for how players get put into this field.
• x and y – These (x,y) coordinates represent the location where the ball was rebounded. It’s common for a ball to bounce around while the player’s try to get the rebound, so understand that this coordinate represents the location where the ball was finally controlled, not where it first landed (or first made contact with a player). Also, for coordinate translations, the shooting team is always considered the offensive team.

Fouls

The only other data being tracked in association with fouls in addition to the (x,y) coordinates is shot-related information for shooting fouls (like assists and pick assists).

• x and y – These (x,y) coordinates represent the location where the foul took place.

Summary

The types above represent what I am tracking. There is a lot more data in the standard play-by-play than the list above, but hopefully that data is straight forward (everyone should know what a block is, for example).

At some point I will create a definition for each field, but for now you will at least understand the intent behind the data I’m tracking.

Please use the comments below to help clarify any questions you might have about the data I’m tracking.