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[1] "<item xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xsi:type=\"itemWithRetweets\" link=\"http://twitter.com/charliekirk11/statuses/1002221842894012416\" id=\"1002221842894012416\">\n  <author>Charlie Kirk</author>\n  <date>2018-05-31T12:14:42-04:00</date>\n  <attachments/>\n  <estimated_retweets>30</estimated_retweets>\n  <screenName>charliekirk11</screenName>\n  <avatarUrl>http://pbs.twimg.com/profile_images/993982887635685377/4CEEsYDS_normal.jpg</avatarUrl>\n  <language>en</language>\n  <location>\n    <country>US</country>\n    <locationString>Chicago, Illinois</locationString>\n  </location>\n</item>"
[2] "<item xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xsi:type=\"itemWithRetweets\" link=\"http://twitter.com/charliekirk11/statuses/1002221842894012416\" id=\"1002221842894012416\">\n  <author>Charlie Kirk</author>\n  <date>2018-05-31T12:14:42-04:00</date>\n  <attachments/>\n  <estimated_retweets>30</estimated_retweets>\n  <screenName>charliekirk11</screenName>\n  <avatarUrl>http://pbs.twimg.com/profile_images/993982887635685377/4CEEsYDS_normal.jpg</avatarUrl>\n  <language>en</language>\n  <location>\n    <country>US</country>\n    <locationString>Chicago, Illinois</locationString>\n  </location>\n</item>"
[3] "<item xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xsi:type=\"itemWithRetweets\" link=\"http://twitter.com/charliekirk11/statuses/1002221842894012416\" id=\"1002221842894012416\">\n  <author>Charlie Kirk</author>\n  <date>2018-05-31T12:14:42-04:00</date>\n  <attachments/>\n  <estimated_retweets>30</estimated_retweets>\n  <screenName>charliekirk11</screenName>\n  <avatarUrl>http://pbs.twimg.com/profile_images/993982887635685377/4CEEsYDS_normal.jpg</avatarUrl>\n  <language>en</language>\n  <location>\n    <country>US</country>\n    <locationString>Chicago, Illinois</locationString>\n  </location>\n</item>"

我有一个 url 列表，想只抓取“link”和“id”。我试过 xml_attr(x, "link) 和 xml_attr(x, "id") 但它似乎不适用于列表。

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1 回答 1

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一种解决方案是使用purrr来自 tidyverse 的包。

基本上，map函数允许您遍历列表、应用函数并取回列表。在这里，我解析了 xml 并以 tibble (data.frame like) 格式整理了值。map_dfr将通过行绑定直接将结果列表转换为表格格式。

xml_text <- list("<item xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xsi:type=\"itemWithRetweets\" link=\"http://twitter.com/charliekirk11/statuses/1002221842894012416\" id=\"1002221842894012416\">\n  <author>Charlie Kirk</author>\n  <date>2018-05-31T12:14:42-04:00</date>\n  <attachments/>\n  <estimated_retweets>30</estimated_retweets>\n  <screenName>charliekirk11</screenName>\n  <avatarUrl>http://pbs.twimg.com/profile_images/993982887635685377/4CEEsYDS_normal.jpg</avatarUrl>\n  <language>en</language>\n  <location>\n    <country>US</country>\n    <locationString>Chicago, Illinois</locationString>\n  </location>\n</item>",
"<item xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xsi:type=\"itemWithRetweets\" link=\"http://twitter.com/charliekirk11/statuses/1002221842894012416\" id=\"1002221842894012416\">\n  <author>Charlie Kirk</author>\n  <date>2018-05-31T12:14:42-04:00</date>\n  <attachments/>\n  <estimated_retweets>30</estimated_retweets>\n  <screenName>charliekirk11</screenName>\n  <avatarUrl>http://pbs.twimg.com/profile_images/993982887635685377/4CEEsYDS_normal.jpg</avatarUrl>\n  <language>en</language>\n  <location>\n    <country>US</country>\n    <locationString>Chicago, Illinois</locationString>\n  </location>\n</item>",
"<item xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xsi:type=\"itemWithRetweets\" link=\"http://twitter.com/charliekirk11/statuses/1002221842894012416\" id=\"1002221842894012416\">\n  <author>Charlie Kirk</author>\n  <date>2018-05-31T12:14:42-04:00</date>\n  <attachments/>\n  <estimated_retweets>30</estimated_retweets>\n  <screenName>charliekirk11</screenName>\n  <avatarUrl>http://pbs.twimg.com/profile_images/993982887635685377/4CEEsYDS_normal.jpg</avatarUrl>\n  <language>en</language>\n  <location>\n    <country>US</country>\n    <locationString>Chicago, Illinois</locationString>\n  </location>\n</item>")

library(xml2)
library(tibble)
library(purrr)
xml_text %>% 
  map_dfr(~ {
    content <- read_xml(.x)
    tibble(
      link = xml_attr(content, "link"),
      id = xml_attr(content, "id")
    )
  })
#> # A tibble: 3 x 2
#>   link                                                          id        
#>   <chr>                                                         <chr>     
#> 1 http://twitter.com/charliekirk11/statuses/1002221842894012416 100222184~
#> 2 http://twitter.com/charliekirk11/statuses/1002221842894012416 100222184~
#> 3 http://twitter.com/charliekirk11/statuses/1002221842894012416 100222184~

由reprex 包（v0.2.0）于 2018 年 6 月 6 日创建。

于 2018-06-06T06:05:52.623 回答