在 R 中创建嵌套列表

Question

我有一个如下的数据框：

df <- data.frame(child = c('item3-1-1','item3-1-2','item3-2','item3-1','item2-1','item2-2','item1'),parent = c('item3-1','item3-1','item3','item3','item2','item2',''))

我想将此数据帧转换为以下格式：

choices <- 

list(
list(id = 1, title = "item1"),

list(id = 2, title = "item2", 

   subs = list(
     list(id = 21, title = "item2-1"), 
     list(id = 22, title = "item2-2")
   )
), 

list(id = 3, title = "item3",
   subs = list(
     list(id = 31, title = "item3-1", isSelectable = FALSE,
          subs = list(
            list(id = 311, title = "item3-1-1"),
            list(id = 312, title = "item3-1-2")
          )
     ),
     list(id = 32, title = "item3-2")
   )
 )
 )

我需要带有“subs”选项的嵌套列表来遍历树下拉列表。

由于我拥有庞大的数据集，是否有任何功能或方法可以实现这一点。

Answer 1

这是一个生成嵌套列表的函数。 id 不一样，但无论如何我们不会在 ComboTree 中使用它们（但它们是必需的）。

dat <- data.frame(
  item = c("item1", "item2", "item2-1", "item2-2", "item3", "item3-1", 
           "item3-1-1", "item3-1-2", "item3-2"), 
  parent = c("root", "root", "item2", "item2", "root", "item3", 
             "item3-1", "item3-1", "item3"),
  stringsAsFactors = FALSE
)

makeChoices <- function(dat){
  f <- function(parent, id = "id"){
    i <- match(parent, dat$item)
    title <- dat$item[i]
    subs <- dat$item[dat$parent==title]
    if(length(subs)){
      list(
        title = title, 
        id = paste0(id,"-",i), 
        subs = lapply(subs, f, id = paste0(id,"-",i))
      )
    }else{
      list(title = title, id = paste0(id,"-",i))
    }
  }
  lapply(dat$item[dat$parent == "root"], f)
}

choices <- makeChoices(dat)

---

> jsonlite::toJSON(choices, auto_unbox = TRUE, pretty = TRUE)
[
  {
    "title": "item1",
    "id": "id-1"
  },
  {
    "title": "item2",
    "id": "id-2",
    "subs": [
      {
        "title": "item2-1",
        "id": "id-2-3"
      },
      {
        "title": "item2-2",
        "id": "id-2-4"
      }
    ]
  },
  {
    "title": "item3",
    "id": "id-5",
    "subs": [
      {
        "title": "item3-1",
        "id": "id-5-6",
        "subs": [
          {
            "title": "item3-1-1",
            "id": "id-5-6-7"
          },
          {
            "title": "item3-1-2",
            "id": "id-5-6-8"
          }
        ]
      },
      {
        "title": "item3-2",
        "id": "id-5-9"
      }
    ]
  }
]