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我有一堆envelope元素的 XML。每个内部都是一个数组。数组中的每一行都有 2 个元素。第一个是标识符，第二个是我要抓取的文本。我需要行的第一个值来识别正确的行，以便我可以获取正确的值。

在下面的示例中，我在用代码表示的行中有“食物” 610954。我想抓住这段代码之后的 2 个元素（c('pizza', 'burger')。同样有代码表示的“饮料” 605380。我想抓住c('coke', 'pepsi')。我怎样才能使用xml2包来做到这一点？

library(xml2)
library(magrittr)

myxml <- read_xml('
<inside>
 <envelope>
  <card-entries type="array">
     <card-entry>
       <card-id type="integer">605380</card-id>
       <value>coke</value>
     </card-entry>
     <card-entry>
       <card-id type="integer">610954</card-id>
       <value>pizza</value>
     </card-entry>  
   </card-entries>
 </envelope>
 <envelope>
  <card-entries type="array">
     <card-entry>
       <card-id type="integer">605380</card-id>
       <value>pepsi</value>
     </card-entry>
     <card-entry>
       <card-id type="integer">610954</card-id>
       <value>burger</value>
     </card-entry>  
   </card-entries>
 </envelope>
</inside>
'
)

## as far as I can parse it (but not specific enough)
myxml %>%
    xml_find_all('//envelope/card-entries[@type="array"]/card-entry') %>%
    xml_text()

food <- -CODE THAT GIVES HERE c('pizza', 'burger')- # 610954
drinks <- -CODE THAT GIVES HERE c('coke', 'pepsi')- # 605380
4

2 回答 2

3

您可以像这样修改您的原始方法以获取饮料：

myxml %>%
  xml_find_all('//envelope/card-entries[@type="array"]/card-entry[card-id = "605380"]/value') %>%
  xml_text()
#[1] "coke"  "pepsi"

但是您可以采用多种其他方法

# get following sibling called value
myxml %>% 
  # foods
  xml_find_all('//card-id[text()="610954"]/following-sibling::value') %>%
  xml_text()
#[1] "pizza"  "burger"

# get following::value[1] - Specify [1] or you would get all following values, 
# including "pepsi".  With value[1] you get only the following value.
myxml %>% 
  # foods
  xml_find_all('//card-id[text()="610954"]/following::value[1]') %>%
  xml_text()
#[1] "pizza"  "burger"

# look for value nodes with a preceding sibling with the appropriate card-id
myxml %>% 
  # drinks
  xml_find_all('//value[preceding-sibling::card-id[text()="605380"]]') %>%
  xml_text()
#[1] "coke"  "pepsi"

# Get value node that is a child of card-entry nodes with the appropriate card-id.
# specifically looking in envelope elements
myxml %>% 
  # drinks
  xml_find_all('//envelope/card-entries/card-entry[card-id = "605380"]/value') %>%
  xml_text()
#[1] "coke"  "pepsi"

# less specific
myxml %>% 
  xml_find_all('//card-entry[card-id = "605380"]/value') %>%
  xml_text()
#[1] "coke"  "pepsi"
于 2017-01-06T21:04:01.037 回答
2

怎么样：

library(tidyverse)
library(stringr)
myxml %>%
  xml_find_all('//envelope/card-entries[@type="array"]/card-entry') %>%
  xml_text() %>% 
  map(.f = str_sub, start = c(1, 7), end = c(6, 1000000L)) %>% 
  reduce(rbind) %>% 
  as_tibble() %>% 
  mutate(type = ifelse(V1 == 605380, yes = "drinks", no = "food"))

然后您可以轻松地将饮料和食物分开划分。

于 2017-01-06T21:21:19.113 回答