如何从嵌套列表中提取特定项目并附加到新列？

Question

我有一个数据框，其中有一列包含嵌套列表。我正在努力从这些嵌套列表中提取用户名（我对此很陌生）。

虚拟数据：

myNestedList <- list("1" = list('username' = "test",
                              "uninteresting data" = "uninteresting content"),
                     "2" = list('username' = "test2",
                                "uninteresting data" = "uninteresting content"))
Column1 <- c("A","B","C")
column2 <- c("a","b","c")
mydf <- data.frame(Column1, column2)
mydf$nestedlist <- list(myNestedList)

我想提取每一行的所有用户名并将它们附加到一个新列中，如果一行有多个用户名，则第二个/第三个/第 n 个用户名应该附加一个分隔符 ", ”。 我尝试过类似sapply(mydf$nestedlist, [[, 1) 之类的东西，但这只是给了我整个列“nestedlist”的一个列表。

对于上下文：我正在尝试构建一个有向图，以便在 Networkx 或 Gephi 中进一步使用。 column1 中的数据是节点，用户名是提及，因此是边。如果有其他方法可以做到这一点，而不是从嵌套列表中提取用户名，这也可能是一种解决方案。

提前感谢您的帮助！ :)

Answer 1

如果我们知道嵌套层次，可以使用map_depth

library(purrr)
 mydf$username <- map_depth(mydf$nestedlist, 2, pluck, "username")

-输出

> mydf
  Column1 column2                                                nestedlist    username
1       A       a test, uninteresting content, test2, uninteresting content test, test2
2       B       b test, uninteresting content, test2, uninteresting content test, test2
3       C       c test, uninteresting content, test2, uninteresting content test, test2

---

或者如果不知道，则使用带有condition 检查的递归函数来查找“用户名”

library(rrapply)
mydf$username <- rrapply(mydf$nestedlist,  
    condition = function(x, .xname) .xname %in% 'username', how = 'prune')
> mydf
  Column1 column2                                                nestedlist    username
1       A       a test, uninteresting content, test2, uninteresting content test, test2
2       B       b test, uninteresting content, test2, uninteresting content test, test2
3       C       c test, uninteresting content, test2, uninteresting content test, test2

---

如果我们想paste他们，请使用

library(stringr)
library(dplyr)
mydf$username <- rrapply(mydf$nestedlist,  
    condition = function(x, .xname) .xname %in% 'username',
          how = 'bind') %>% 
        invoke(str_c, sep=", ", .)
 mydf
  Column1 column2                                                nestedlist    username
1       A       a test, uninteresting content, test2, uninteresting content test, test2
2       B       b test, uninteresting content, test2, uninteresting content test, test2
3       C       c test, uninteresting content, test2, uninteresting content test, test2

-结构

> str(mydf)
'data.frame':   3 obs. of  4 variables:
 $ Column1   : chr  "A" "B" "C"
 $ column2   : chr  "a" "b" "c"
 $ nestedlist:List of 3
  ..$ :List of 2
  .. ..$ 1:List of 2
  .. .. ..$ username          : chr "test"
  .. .. ..$ uninteresting data: chr "uninteresting content"
  .. ..$ 2:List of 2
  .. .. ..$ username          : chr "test2"
  .. .. ..$ uninteresting data: chr "uninteresting content"
  ..$ :List of 2
  .. ..$ 1:List of 2
  .. .. ..$ username          : chr "test"
  .. .. ..$ uninteresting data: chr "uninteresting content"
  .. ..$ 2:List of 2
  .. .. ..$ username          : chr "test2"
  .. .. ..$ uninteresting data: chr "uninteresting content"
  ..$ :List of 2
  .. ..$ 1:List of 2
  .. .. ..$ username          : chr "test"
  .. .. ..$ uninteresting data: chr "uninteresting content"
  .. ..$ 2:List of 2
  .. .. ..$ username          : chr "test2"
  .. .. ..$ uninteresting data: chr "uninteresting content"
 $ username  : chr  "test, test2" "test, test2" "test, test2"