How to compute special teams epa split by kicking and receiving

special_teams_epa.R

library(dplyr)

st_plays <- nflreadr::load_pbp(2021) |>
  filter(!is.na(epa) & touchback != 1 & special == 1)

epa_kicking <- st_plays |>
  group_by(team = posteam) |>
  mutate(epa = dplyr::if_else(play_type == "kickoff", -epa, epa)) |>
  summarize(epa_kick = mean(epa), plays_kick = n())

epa_receiving <- st_plays |>
  group_by(team = defteam) |>
  mutate(epa = dplyr::if_else(play_type == "kickoff", epa, -epa)) |>
  summarize(epa_receive = mean(epa), plays_receive = n())

epa <- epa_kicking |>
  left_join(epa_receiving, by = "team") |>
  mutate(
    epa_combined = (epa_kick * plays_kick + epa_receive * plays_receive) / (plays_kick + plays_receive),
    plays_combined = plays_kick + plays_receive
  ) |>
  inner_join(nflfastR::teams_colors_logos, by = c("team" = "team_abbr")) |>
  arrange(desc(epa_combined))