4.3 Rate Statistics

In baseball statistics, consider the use of both count statistics and rate statistics

• count statistics (for example): \(AB\), \(ER\), \(H\), \(IP\)
• rate statistics (for example):

\[BA = \frac{H}{AB}, \quad ERA = \frac{ER}{IP} \cdot 9\]

4.3.1 Win Percentage

ch4_data <- Teams |>
  filter(yearID >= 1998, yearID != 2020) |>
  select(yearID, lgID, teamID, G, W, L, R, RA, DivWin, WCWin) |>
  
  # run differential
  mutate(RD = R - RA) |>
  
  # win percentage
  mutate(Wpct = W / (W + L)) |>
  
  # playoff win (Boolean)
  mutate(playoff_bool = ifelse(
    DivWin == "Y" | WCWin == "Y",
    "made playoffs", "missed playoffs"
  ))