折叠列表列元素到字符串

Question

我想将一个子类别折叠成一个逗号的字符串以进行显示。
这就是我所拥有的。

library(tibble)
eats <- tribble(
  ~food,~variety,
  "fruit","cherry",
  "fruit","apple",
  "fruit","peach",
  "nut","cashew",
  "nut","almonds"
)
eats
#> # A tibble: 5 x 2
#>   food  variety
#>   <chr> <chr>  
#> 1 fruit cherry 
#> 2 fruit apple  
#> 3 fruit peach  
#> 4 nut   cashew 
#> 5 nut   almonds

这就是我想要的：

eats2 <- tribble(
  ~food,~varieties,
  "fruit","cherry, apple, peach",
  "nut","cashew, almond"
)
eats2  
#> # A tibble: 2 x 2
#>   food  varieties           
#>   <chr> <chr>               
#> 1 fruit cherry, apple, peach
#> 2 nut   cashew, almond

我尝试的是：

eats %>% 
  nest(data=variety) %>% 
  mutate(data = paste(data,collapse = ""))
#> # A tibble: 2 x 2
#>   food  data                                                                    
#>   <chr> <chr>                                                                   
#> 1 fruit "list(variety = c(\"cherry\", \"apple\", \"peach\"))list(variety = c(\"~
#> 2 nut   "list(variety = c(\"cherry\", \"apple\", \"peach\"))list(variety = c(\"~

不。

eats %>% 
  nest(data=variety) %>% 
  map(~.x %>% mutate(varieties=paste(data,collapse = "")))
#> Error in UseMethod("mutate"): no applicable method for 'mutate' applied to an object of class "character"

由Reprex软件包（v2.0.1）在2022-07-01创建

。正确的方法是什么？谢谢。

Answer 1

您可以使用总结和toString：

library(tibble)
library(dplyr)
eats <- tribble(
  ~food,~variety,
  "fruit","cherry",
  "fruit","apple",
  "fruit","peach",
  "nut","cashew",
  "nut","almonds"
)
eats %>%
  group_by(food) %>%
  summarise(varieties = toString(variety)) %>%
  ungroup()
#> # A tibble: 2 × 2
#>   food  varieties           
#>   <chr> <chr>               
#> 1 fruit cherry, apple, peach
#> 2 nut   cashew, almonds

^{在2022-07-01创建的 reprex软件包（v2.0.1）}

Answer 2

就像 @quinten的解决方案一样，只需使用粘贴而不是toString：

library(dplyr)

eats %>%
  group_by(food) %>%
  summarise(varieties = paste(variety, collapse = ", ")) %>%
  ungroup()

  food  varieties           
  <chr> <chr>               
1 fruit cherry, apple, peach
2 nut   cashew, almonds