r - 按字母顺序在两列中创建组合信息的新列

Question

我有一个足球队数据集，如下所示:

Home_team Away_team Home_score Away_score
Arsenal    Chelsea      1        3
Manchester U  Blackburn 2        9
Liverpool      Leeds    0        8
Chelsea     Arsenal     4        1

我想对所涉及的球队进行分组，无论哪支球队在主场和客场比赛。例如，如果切尔西对阵阿森纳，无论比赛是在切尔西还是在阿森纳，我都希望新列“teams_involved”是阿森纳 - 切尔西。我的猜测是这样做的方法是按字母顺序将这些团队添加到新列中，但我不知道该怎么做。

期望的输出:

Home_team Away_team Home_score Away_score teams_involved
Arsenal    Chelsea      1        3     Arsenal - Chelsea
Manchester U  Blackburn 2        9   Blackburn - Manchester U
Liverpool      Leeds    0        8      Leeds - Liverpool 
Chelsea     Arsenal     4        1     Arsenal - Chelsea

我之所以要这样做，是因为我可以看到每支球队对阵特定球队的胜利次数，无论比赛地点如何。

Answer 1

df = read.table(text = "
Home_team Away_team Home_score Away_score
Arsenal    Chelsea      1        3
ManchesterU  Blackburn 2        9
Liverpool      Leeds    0        8
Chelsea     Arsenal     4        1
", header=T, stringsAsFactors=F)

library(dplyr)

df %>%
  rowwise() %>%      # for each row
  mutate(Teams = paste(sort(c(Home_team, Away_team)), collapse = " - ")) %>%  # sort the teams alphabetically and then combine them separating with -
  ungroup()          # forget the row grouping

# # A tibble: 4 x 5
#   Home_team   Away_team Home_score Away_score Teams                  
#   <chr>       <chr>          <int>      <int> <chr>                  
# 1 Arsenal     Chelsea            1          3 Arsenal - Chelsea      
# 2 ManchesterU Blackburn          2          9 Blackburn - ManchesterU
# 3 Liverpool   Leeds              0          8 Leeds - Liverpool      
# 4 Chelsea     Arsenal            4          1 Arsenal - Chelsea 

没有 rowwise 的替代解决方案:

# create function and vectorize it
f = function(x,y) {paste(sort(c(x, y)), collapse = " - ")}
f = Vectorize(f)

# apply function to your dataset
df %>% mutate(Teams = f(Home_team, Away_team))