R语言使用dplyr的summarize统计分组后样本出现次数

你要统计每支球队作为主队的参赛场次，直接调用dplyr的n()函数即可，该函数会返回每个分组的行数，刚好对应球队的分组参赛场数。注意带空格的字段名需要用反引号包裹，才能被R识别为合法变量名。

修改后的主队统计代码如下：

new_df <- df %>%
  group_by(home_team_name) %>%
  summarize(
    stat1 = mean(stat1),
    `games played` = n()
  )

如果要统计球队作为客队的参赛场次，只需修改分组字段即可：

away_df <- df %>%
  group_by(away_team_name) %>%
  summarize(
    stat1 = mean(stat1),
    `games played` = n()
  )

如果需要同时汇总单支球队的主客场总数据，可以先把数据转为长格式再分组统计，代码示例如下：

library(tidyr)
total_df <- df %>%
  pivot_longer(cols = c(home_team_name, away_team_name), 
               names_to = "home_away", 
               values_to = "team_name") %>%
  group_by(team_name, home_away) %>%
  summarize(
    stat1 = mean(stat1),
    `games played` = n(),
    .groups = "drop"
  )

内容的提问来源于stack exchange，提问作者jprice