Ball park effects (reprise)

• Compute home and away HRs for each team
• Compute park factor as ratio of home HRs to away HRs.

sc_home <- sc_2023 |> 
  group_by(home_team) |> 
  summarize(HR = sum(HR))
sc_away <- sc_2023 |> 
  group_by(away_team) |> 
  summarize(HR = sum(HR))
pf <- sc_home |>
  inner_join(sc_away, join_by(home_team == away_team)) |> 
  mutate(Park_Factor = HR.x / HR.y)