Method · lineup_stability@v1

Lineup stability

For each hitter, the number of different batting-order slots he was used in across the season, and his average slot. A player used in two or three slots has a defined job. A player used in all nine does not.

The filter, exactly as it runs

lineup_slot BETWEEN 1 AND 9

Parameters

min_starts 50

Where this is arguable

Churn can be an effect rather than a cause: a hitter who slumps gets moved down, so instability may be the manager reacting rather than the manager creating. The way to test it is to compare players at similar production levels, which is what this piece does.
Injuries and days off force changes nobody chose. A club with a banged-up roster will look less stable than one that stayed healthy.
Some managers deliberately move hitters to exploit matchups, which is a defensible plan and looks identical to churn here.

These are the objections I already know about. If you have a better one, or you think a different threshold tells a truer story, say so and I will re-run it with your numbers and publish what comes back.

Version 1. Older versions are never deleted, so a piece that citeslineup_stability@v1 stays reproducible after this definition is revised. Source: Data: nflverse (nflfastR), CC-BY 4.0