Tóm tắt theo nhóm về mức độ thiếu dữ liệu

# `bind_shadow()` and `group_by()` humidity missingness (`humidity_NA`)
oceanbuoys %>%
  ___() %>%
  group_by(___) %>% 
  summarize(wind_ew_mean = mean(___), # calculate mean of wind_ew
            wind_ew_sd = ___)) # calculate standard deviation of wind_ew
  
# Repeat this, but calculating summaries for wind north south (`wind_ns`).
___ %>%
  ___ %>%
  group_by(___) %>%
  summarize(___ = ___(___),
            ___ = ___(___))