使用 dplyr 计算多个分组变量

Question

我有一个包含多个分类变量的数据集

data <- data_frame(
HomeTeam = c("Team1", "Team2", "Team3", "Team4", "Team2", "Team2", "Team4", 
             "Team3", "Team2", "Team1", "Team3", "Team2"),
AwayTeam = c("Team2", "Team1", "Team4", "Team3", "Team1", "Team4", "Team1", 
             "Team2", "Team3", "Team3", "Team4", "Team1"),
HomeScore = c(10, 5, 12, 18, 17, 19, 23, 17, 34, 19, 8, 3),
AwayScore = c(4, 16, 9, 19, 16, 4, 8, 21, 6, 5, 9, 17),
Venue = c("Ground1", "Ground2", "Ground3", "Ground3", "Ground1", "Ground2", 
          "Ground1", "Ground3", "Ground2", "Ground3", "Ground4", "Ground2"))

我基本上想通过计数将“HomeTeam”和“AwayTeam”汇总到一个新表中，如下所示

 HomeTeam NumberOfGamesHome NumberOfGamesaWAY
 <chr>                <int>             <int>
 1 Team1                    2                 4
 2 Team2                    5                 2
 3 Team3                    3                 3
 4 Team4                    2                 3

我目前的方法需要两行分组代码，然后加入表格

HomeTeamCount <- data %>% 
group_by(HomeTeam) %>% 
summarise(NumberOfGamesHome = n()) 

AwayTeamCount <- data %>% 
group_by(AwayTeam) %>% 
summarise(NumberOfGamesAway = n()) 

Desired <- left_join(HomeTeamCount, AwayTeamCount, 
                 by = c("HomeTeam" = "AwayTeam"))

在我的实际数据集中，我有大量的分类变量，按照上面的方法似乎很费力，效率低下

有没有办法使用 dplyr 对多个分类变量进行分组，以产生所需的输出？或者可能是 data.table？

我咨询了here和here等其他几个问题，但一直没能找到答案。

Answer 1

这是一种使用gather 将数据从宽向长传播的可能性，按球队分组并汇总主客场比赛的数量。

library(tidyverse)
data %>%
    gather(key, Team) %>%
    group_by(Team) %>%
    summarise(
        NumberOfGamesHome = sum(key == "HomeTeam"),
        NumberOfGamesaWAY = sum(key == "AwayTeam"))
## A tibble: 4 x 3
#  Team  NumberOfGamesHome NumberOfGamesaWAY
#  <chr>             <int>             <int>
#1 Team1                 2                 4
#2 Team2                 5                 2
#3 Team3                 3                 3
#4 Team4                 2                 3

---

更新

要使用其他列反映更新后的示例数据，您可以这样做

data %>%
    gather(key, Team, HomeTeam, AwayTeam) %>%
    group_by(Team) %>%
    summarise(
        NumberOfGamesHome = sum(key == "HomeTeam"),
        NumberOfGamesaWAY = sum(key == "AwayTeam"))
## A tibble: 4 x 3
#  Team  NumberOfGamesHome NumberOfGamesaWAY
#  <chr>             <int>             <int>
#1 Team1                 2                 4
#2 Team2                 5                 2
#3 Team3                 3                 3
#4 Team4                 2                 3