时间戳

首页 > 解决方案 > 循环选择节点并选择第一个节点内任何级别的子节点

r - 循环选择节点并选择第一个节点内任何级别的子节点

问题描述

我正在使用 xml2 包。我想要：

  1. 选择具有特定标签的节点（在本例中为 all envelope）
  2. 循环遍历这些节点并选择其中的节点，而不考虑嵌套（在这种情况下，所有value标签都在card-entry标签内）
  3. 用空格连接文本

有三个信封，所以我希望能够从value标签内找到的card-entry标签内返回一个包含所有文本的三个向量。我无法做到这一点。我怎样才能做到这一点？为什么我下面的方法不起作用？

MWE

library(xml2)

myxml <- read_xml('
<inside>
 <box>
   <card-entry>
     <card-id type="integer">605383</card-id>
     <value>get well</value>
   </card-entry>
 </box>
 <envelope>
     <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-entry>
       <card-id type="integer">605381</card-id>
       <value>surprise</value>
     </card-entry>
     <card-entry>
       <card-id type="integer">610958</card-id>
       <value>joke</value>
       <random>true</random>
     </card-entry> 
 </envelope>
 <envelope>
     <card-entry>
       <card-id type="integer">605381</card-id>
       <value>charlie horse</value>
     </card-entry>
     <card-entry>
       <card-id type="integer">605380</card-id>
       <value>rug bug</value>
     </card-entry>
     <subenvelope>
       <value>dont get me</value>
     </subenvelope>
     <card-entry>
       <card-id type="integer">610954</card-id>
       <value>mario cart</value>
     </card-entry>  
 </envelope>
 <envelope>
     <card-entry>
       <card-id type="integer">605377</card-id>
       <value>trogdor</value>
     </card-entry>
     <subenvelope>
       <card-entry>
         <card-id type="integer"></card-id>
         <value>jorb</value>
       </card-entry>
     </subenvelope>
     <card-entry>
       <card-id type="integer">605333</card-id>
       <value></value>
     </card-entry>    
 </envelope>
</inside>
'
)

期望的输出

## [1] coke pizza surprise joke
## [2] charlie horse rug bug mario cart
## [3] trogdor jorb

我试过的

children <- lapply(xml2::xml_find_all(myxml, '//envelope'), xml2::xml_children)

rm_na <- function(x) x[!is.na(x)]

lapply(children, function(x){

    paste(rm_na(unlist(xml2::xml_text(xml2::xml_child(x, '//card-entry//value')))), collapse = ' ')

})

## [[1]]
## [1] ""
## 
## [[2]]
## [1] ""
## 
## [[3]]
## [1] ""
## 
## There were 11 warnings (use warnings() to see them)


lapply(children, function(x){

    paste(rm_na(unlist(xml2::xml_text(xml2::xml_find_all(x, '//card-entry//value')))), collapse = ' ')

})

## [[1]]
## [1] "get well coke pizza surprise joke charlie horse rug bug mario cart trogdor jorb "
## 
## [[2]]
## [1] "get well coke pizza surprise joke charlie horse rug bug mario cart trogdor jorb "
## 
## [[3]]
## [1] "get well coke pizza surprise joke charlie horse rug bug mario cart trogdor jorb "

标签： rxml2

解决方案

在你的内部选择器上，你想让它相对于当前节点，所以你想要.//而不是//再次搜索整个树

sapply(xml_find_all(myxml,"//envelope"), function(x) 
  paste(xml_text(xml_find_all(x, ".//card-entry/value")), collapse=" ")
)

# [1] "coke pizza surprise joke"        
# [2] "charlie horse rug bug mario cart"
# [3] "trogdor jorb "

推荐阅读