Recipe: Platoon Splits (Batter vs. Pitcher Handedness)

import retrosheetpy as rs
import polars as pl

# 1. Download 2024 play-by-play events
events = rs.events(year=2024, backend="polars")

# 2. Filter for official at-bats
ab_events = events.filter(pl.col("AB_FL") == True)

# 3. Calculate Batting Average and Slugging by Matchup Handedness
splits = (
    ab_events.group_by(["BAT_HAND_CD", "PIT_HAND_CD"])
    .agg(
        [
            pl.len().alias("at_bats"),
            pl.col("H_FL").cast(pl.Int32).sum().alias("hits"),
            pl.col("HR_FL").cast(pl.Int32).sum().alias("home_runs"),
        ]
    )
    .with_columns(
        [
            (pl.col("hits") / pl.col("at_bats")).round(3).alias("batting_avg"),
            (pl.col("home_runs") / pl.col("at_bats")).round(4).alias("hr_rate"),
        ]
    )
    .sort(["BAT_HAND_CD", "PIT_HAND_CD"])
)

print(splits)