r - 从多级嵌套列表中提取信息

Question

我在嵌套列表中有一组数据，这样顶部列表的每个成员都有描述符(但不一定是相同的描述符)，然后是子项列表，这些子项可以有子项，依此类推。 child 的深度是任意的。一个最小的例子:

family <- list(
  list(name = "Alice", age = 40, eyes = "blue", children = list(
    list(name = "Bob", age = 20, eyes = "blue"),
    list(name = "Charlie", age = 18, eyes = "brown")
)), 
  list(name = "Dan", age = 12, eyes = "green"),
  list(name = "Erin", age = 69, eyes = "green", children = list(
    list(name = "Frank", age = 45, eyes = "blue", children = list(
      list(name = "George", age = 24, eyes = "blue", children = list(
        list(name = "Harry", age = 2, eyes = "green")
      )), 

      list(name = "Ingrid", age = 22, eyes = "brown", hair = "brown"),
      list(name = "Jack", age = 29, eyes = "brown")
    )), 
    list(name = "Karen", age = 43),
    list(name = "Larry", age = 21, eyes = "blue")
  )) 
)

> str(family, max.level = 2)
List of 3
 $ :List of 4
  ..$ name    : chr "Alice"
  ..$ age     : num 40
  ..$ eyes    : chr "blue"
  ..$ children:List of 2
 $ :List of 3
  ..$ name: chr "Dan"
  ..$ age : num 12
  ..$ eyes: chr "green"
 $ :List of 4
  ..$ name    : chr "Erin"
  ..$ age     : num 69
  ..$ eyes    : chr "green"
  ..$ children:List of 3

理想情况下，我想创建一个数据框，这样每一行都是一个家庭成员，每一列都是列表中的一个属性:

      name       age      eyes
    1 Alice       40      blue
    2 Bob         20      blue
    3 Charlie     18      brown
(etc)

但是不清楚如何递归地做到任意深度。我设法使用 map(family, ~ .$name) 获得了顶级成员，但我不明白如何更深入。有些成员没有 child ，这让事情变得复杂。

我已经查看了 purrr 文档，但我找不到任何似乎有帮助的内容。也许我没有使用正确的术语。

建议表示赞赏。谢谢!

Answer 1

您始终可以递归地遍历列表并收集信息。除了map_dfr来自 purrr我的解决方案使用 defaults来自 plyr处理缺少眼睛或头发颜色的情况。

get_people <- function(x) {
  if (is.null(x)) return(NULL)
  if (!is.null(x$name)) { # if there's a name, we're at the level of a person
    children <- x$children
    x$children <- NULL
    row <- data.frame(plyr::defaults(x, list(age = NA, eyes = NA, hair = NA)),
                      stringsAsFactors = FALSE)
    rbind(row, get_people(children))
  }
  else {
    purrr::map_dfr(x, get_people)
  }
}

当您将此应用于您的列表时:

> get_people(family)
      name age  eyes  hair
1    Alice  40  blue  <NA>
2      Bob  20  blue  <NA>
3  Charlie  18 brown  <NA>
4      Dan  12 green  <NA>
5     Erin  69 green  <NA>
6    Frank  45  blue  <NA>
7   George  24  blue  <NA>
8    Harry   2 green  <NA>
9   Ingrid  22 brown brown
10    Jack  29 brown  <NA>
11   Karen  43  <NA>  <NA>
12   Larry  21  blue  <NA>