R语言：如何合并两列生成按字母排序的新列FruitsDiff？

现有如下数据集：

ID<-c("A","B","C","D","E")
Fruits1<-c("orange","apple","pineapple","apple","pineapple")
Fruits2<-c("apple","orange","apple","pineapple","orange")
data<-tibble(ID,Fruits1,Fruits2)
data
# A tibble: 5 × 3
ID    Fruits1   Fruits2  
<chr> <chr>     <chr>    
1 A     orange    apple    
2 B     apple     orange   
3 C     pineapple apple    
4 D     apple     pineapple
5 E     pineapple orange  

需要新增一列FruitsDiff，将Fruits1和Fruits2的内容按字母顺序排序后合并——无论原列中水果的先后顺序如何，合并结果都保持一致（比如第1行原顺序是orange在前、apple在后，合并后为apple-orange），分隔符可自定义。

方法1：dplyr + purrr 行级处理 #

用rowwise()对每行单独操作，结合sort()排序后拼接：

library(dplyr)
library(purrr)

data <- data %>%
  rowwise() %>%
  mutate(FruitsDiff = paste(sort(c(Fruits1, Fruits2)), collapse = "-")) %>%
  ungroup()

如果数据存在大小写差异（比如Pineapple和pineapple），可以先统一转小写再排序：

data <- data %>%
  rowwise() %>%
  mutate(FruitsDiff = paste(sort(tolower(c(Fruits1, Fruits2))), collapse = "-")) %>%
  ungroup()

方法2：Base R 原生实现 #

无需额外加载包，用apply()逐行处理：

data$FruitsDiff <- apply(data[, c("Fruits1", "Fruits2")], 1, function(x) {
  paste(sort(x), collapse = "-")
})

处理大小写的版本：

data$FruitsDiff <- apply(data[, c("Fruits1", "Fruits2")], 1, function(x) {
  paste(sort(tolower(x)), collapse = "-")
})

方法3：tidyr 宽转长扩展方案（适配多列场景） #

如果后续需要处理更多水果列，这种方法更灵活：

library(tidyr)
library(dplyr)

data <- data %>%
  pivot_longer(cols = starts_with("Fruits"), names_to = NULL, values_to = "fruit") %>%
  mutate(fruit = tolower(fruit)) %>%
  group_by(ID) %>%
  arrange(fruit, .by_group = TRUE) %>%
  summarise(FruitsDiff = paste(fruit, collapse = "-"), .groups = "drop") %>%
  left_join(data, by = "ID") %>%
  select(ID, Fruits1, Fruits2, FruitsDiff)

运行后可得到目标结果：

# A tibble: 5 × 4
ID    Fruits1   Fruits2   FruitsDiff      
<chr> <chr>     <chr>     <chr>           
1 A     orange    apple     apple-orange    
2 B     apple     orange    apple-orange    
3 C     pineapple apple     apple-pineapple 
4 D     apple     pineapple apple-pineapple 
5 E     pineapple orange    orange-pineapple

内容的提问来源于stack exchange，提问作者Cam