wPDI & CSW: Residuals
Introduction
This is the third article in my series – wPDI & CSW. You can catch up by reading the first two articles – on called strikes and whiffs – found here and here.
Here is a quick recap of what we have covered so far:
In this series, we are looking at the PitcherList metric, CSW and how it relates to my plate discipline framework, wPDI. Last year’s FSWA Research Article of the Year by Alex Fast featured CSW, which is defined as:
Called Strikes + Whiffs
Total Pitches
With the Weighted Plate Discipline Index (wPDI) framework, all pitches are classified into six different outcomes as follows:
Outcome | Outcome | Outcome | Outcome | Outcome | Outcome | |
---|---|---|---|---|---|---|
A | B | C | D | E | F | |
Zone? | Out of Zone | Out of Zone | Out of Zone | In Zone | In Zone | In Zone |
Swing? | Swung On | Swung On | No Swing | Swung On | Swung On | No Swing |
Contact? | No Contact | Contact Made | No Swing | No Contact | Contact Made | No Swing |
Each outcome is then assigned a weight, or an index. A% through F% are the percent of pitches thrown in each outcome. The general formula for wPDI, the Weighted Plate Discipline Index is given as:
wPDI = IndexA * A% + IndexB * B% + IndexC * C% + IndexD * D% + IndexE * E% + IndexF * F%