如何在 dplyr 和 R 中匯總和子集多級分組 dataframe

Question

我有以下長格式數據：

testdf <- tibble(
          name = c(rep("john", 4), rep("joe", 2)), 
          rep = c(1, 1, 2, 2, 1, 1), 
          field = rep(c("pet", "age"), 3), 
          value = c("dog", "young", "cat", "old", "fish", "young")
)

對於每個命名的人（約翰和喬），我想總結一下他們的每只寵物：
出於某種原因，我似乎無法處理“約翰”數據中的重復事件/寵物。
如果我只為 Joe（只有一只寵物）過濾，則代碼有效。

非常感謝任何幫助......

testdf %>%
          group_by(name, rep) %>%
        #  filter(name == "joe") %>%  # when I filter only for Joe, the code works
          summarise(
                    about = paste0(
                              "The pet is a: ", .[field == "pet", "value"], " and it is ", .[field == "age", "value"]
                    )
          )

Answer 1

testdf %>%
  pivot_wider(id_cols = name:rep,names_from = field) %>% 
  mutate(about = paste0("The pet is a: ", pet, " and it is ", age))

  name    rep pet   age   about                             
  <chr> <dbl> <chr> <chr> <chr>                             
1 john      1 dog   young The pet is a: dog and it is young 
2 john      2 cat   old   The pet is a: cat and it is old   
3 joe       1 fish  young The pet is a: fish and it is young

這也可以用data.table來完成，如下：

library(data.table)

setDT(testdf)[
  ,j = .(about = paste0("The pet is a ", .SD[field=="pet",value], " and it is ", .SD[field=="age",value])),
  by = .(name,rep)
]

   name rep                             about
1: john   1  The pet is a dog and it is young
2: john   2    The pet is a cat and it is old
3:  joe   1 The pet is a fish and it is young

Answer 2

您的數據是長格式且不整齊，多個字段合而為一。 所以傳播它或 pivot 更廣泛是 langtang 回答的。 （更好的是 data.table 但我發現仍然很難使用.SD]

我更喜歡在 dplyr 中盡可能簡單地做這些事情。另一種不傳播的方法如下，它會產生相同的結果。 [沒有 data.table where.SD 對我來說仍然很難掌握：所以在 3 行中：

testdf%>%
  group_by(name,rep)%>%    
  summarise(about = paste("The pet is ",value[field=='pet']," and it is ",value[field=='age']))

產量：

      name    rep about                             
  <chr> <dbl> <chr>                             
1 joe       1 The pet is  fish  and it is  young
2 john      1 The pet is  dog  and it is  young 
3 john      2 The pet is  cat  and it is  old