您可以取消嵌套countries，然后删除重复的行。

library(tidyverse)

df %>%
  unnest(countries) %>%
  distinct()

# # A tibble: 2 × 2
#   class          countries     
#   <chr>          <chr>         
# 1 Großbrittanien United Kingdom
# 2 Rest Europa    Spain

或者不使用unnest，在转换为字符串之前按类使用unique。

• • 分组：**

library(dplyr)

df |>
  mutate(countries = toString(unique(unlist(countries))), .by = class)

# Note: If you're using `dplyr < v.1.1.0`, use `group_by`/`ungroup`.

• • 使用purrr：**

library(dplyr)
library(purrr)

df |>
  mutate(countries = map_chr(countries, ~ toString(unique(.))))

• • 输出：**

# A tibble: 2 × 2
  class          countries     
  <chr>          <chr>         
1 Großbrittanien United Kingdom
2 Rest Europa    Spain, Portugal

• • 数据（包括不重复的内容..葡萄牙）：**

df <- 
  structure(list(class = c("Großbrittanien", "Rest Europa"), countries = list(
    c("United Kingdom", "United Kingdom"), c("Spain", "Portugal"))), row.names = c(NA, 
                                                                    -2L), class = c("tbl_df", "tbl", "data.frame"))

以下是使用dplyr语法的版本

library(dplyr)

df %>%
  unnest(countries) %>%
  distinct(class, countries) %>%
  group_by(class) %>%
  summarise(countries = paste(countries, collapse = ", "))