Fourth Down Bot

This is the code that powers the New York Times 4th Down Bot. Using NFL play-by-play data from Armchair Analysis, this code will:

• Munge the raw play-by-play data and transform it into a form suitable for modeling
• Create a win probability model and serialize that model
• Provide all of the functions to make optimal 4th down decisions for a given play

The Armchair Analysis data is not free. It costs $49 (one-time) to gain access to play-by-play data from the 2000-2014 NFL seasons. There is also a professional package that will provide weekly updates. Without the Armchair Analysis data, you will not be able to use much of this code.

This code currently requires Python 2.7 and is not Python 3 compliant to our knowledge. Questions about the Python code can be directed to Trey Causey.

Please note that none of the file operations are supported on Windows.

NOTE: If you are unable to purchase the Armchair Analysis data, Ben Dilday has created a fork of this code that uses freely available play-by-play data. There are no guarantees that this fork is current with the production version of the 4th Down Bot and this fork is not affiliated in any way with or supported by The Upshot or Trey Causey. You can find that fork here. Questions about that fork should be directed to Ben Dilday.

Python package requirements

• click
• matplotlib (if you want to visually diagnose your model's performance)
• naked
• numpy
• pandas
• scikit-learn

Usage

Unzip the play-by-play data into a directory. Run the following code from the directory where you want the Fourth Down Bot code to live. It will create the subdirectories models and data to store files.

python data_prep.py <pbp data dir>
python model_train.py

If you wish to view the calibration plots and ROC curves for the model, run model_train with the --plot flag, like so:

python model_train.py --plot

There is a rudimentary command line interface for interactively querying the bot's model, although the model was built to be queried programatically. Feel free to improve upon this. To query the model interactively, use the following syntax at the command line and follow the prompts:

python bot.py

Field goal model

The bot's field goal model is also accessible as a separate module, via either a node script (see model-fg/example.js for details) or the command line. A sample query:

node model-fg/model-fg.js --kicker_code=AH-2600 --temp=40 --wind=10 --yfog=67 --chanceOfRain=10 --is_dome=1 --is_turf=0

As an alternative to supplying the Armchair Analysis player code, you can instead specify the team on offense (team codes are fairly standard, but see model-fg.js for a lookup table). Similarly, you can supply the home team instead of is_dome and is_turf arguments:

node model-fg/model-fg.js --offense=PHI --home=NE --temp=40 --wind=10 --yfog=67 --chanceOfRain=10