从嵌套列表中提取具有特定名称的所有元素 [英] pull all elements with specific name from a nested list

问题描述

我有一些存档的 Slack 数据，我正在尝试获取一些关键消息属性.我通过愚蠢地展平整个列表，获得一个 data.frame 或带有嵌套在某些单元格中的列表的 tibble 来做到这一点.随着这个数据集越来越大，我想更聪明地从这个列表中挑选元素，这样当这个缓存变大时，它不会永远用我想要的元素来创建 data.frame 或 tibble.

I have some archived Slack data that I am trying to get some of key message properties. I'd done this by stupidly flattening the entire list, getting a data.frame or tibble with lists nested in some cells. As this dataset gets bigger, I want to pick elements out of this list more smartly so that when this cache becomes big it doesn't take forever to create the data.frame or tibble with the elements I want.

我试图拉取名为type"的所有内容的示例下面进入一个向量或平面列表，我可以将其作为数据帧变量引入.为方便起见，我命名了文件夹和消息级别.任何人都有可以提供帮助的模型代码?

Example where I am trying to pull everything named "type" below into a vector or flat list that I can pull in as a dataframe variable. I named the folder and message level for convenience. Anyone have model code that can help?

library(tidyverse)
    
l <- list(folder_1 = list(
  `msg_1-1` = list(type = "message",
               subtype = "channel_join",
               ts = "1585771048.000200",
               user = "UFUNNF8MA",
               text = "<@UFUNNF8MA> has joined the channel"),
  `msg_1-2` = list(type = "message",
                   subtype = "channel_purpose",
                   ts = "1585771049.000300",
                   user = "UNFUNQ8MA",
                   text = "<@UNFUNQ8MA> set the channel purpose: Talk about xyz")),
  folder_2 = list(
    `msg_2-1` = list(type = "message",
                  subtype = "channel_join",
                  ts = "1585771120.000200",
                  user = "UQKUNF8MA",
                  text = "<@UQKUNF8MA> has joined the channel")) 
)

# gets a specific element
print(l[[1]][[1]][["type"]])

# tried to get all elements named "type", but am not at the right list level to do so
print(purrr::map(l, "type"))

推荐答案

与@Duck & 提供的相关@Abdessabour Mtk 昨天，purrr 有一个函数 map_depth() ，如果您知道它的名称以及它在层次结构中的深度，它将让您获得一个命名属性.在抓取这个大型嵌套列表时非常有用，并且是上面嵌套 map() 调用的更简单的解决方案.

Related to those provided by @Duck & @Abdessabour Mtk yesterday, purrr has a function map_depth() that will let you get a named attribute if you know its name and how deep it is in the hierarchy. REALLY useful when crawling this big nested lists, and is a simpler solution to the nested map() calls above.

purrr::map_depth(l, 2, "type")

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