从xml文件获取嵌套数据

我有一个

xml

文件，其结构如下：

<?xml version="1.0" encoding="utf-8"?>
<ScheduleMessage DtdVersion="3" DtdRelease="0">
  <MessageIdentification v="ETSOVista-DMinus1TotalLoadForecast-DE-2012-1" />
  <MessageVersion v="1" />
  <MessageType v="A11" />
    <ScheduleTimeSeries>
    <SendersTimeSeriesIdentification v="10YCB-GERMANY--8" />
    <SendersTimeSeriesVersion v="1" />
    <BusinessType v="A05" />
    <Period>
      <TimeInterval v="2012-11-15T23:00Z/2012-11-16T23:00Z" />
      <Resolution v="PT60M" />
      <Interval>
        <Pos v="1" />
        <Qty v="52452" />
      </Interval>
      <Interval>
        <Pos v="2" />
        <Qty v="50527" />
      </Interval>
      <Interval>
       <Pos v="3" />
       <Qty v="49221" />
      </Interval>
      <Interval>
       <Pos v="4" />
       <Qty v="49344" />
      </Interval>
    </Period>
   </ScheduleTimeSeries>
   <ScheduleTimeSeries>
    <SendersTimeSeriesIdentification v="10YCB-GERMANY--8" />
    <SendersTimeSeriesVersion v="1" />
    <BusinessType v="A05" />
    <Period>
     <TimeInterval v="2012-11-16T23:00Z/2012-11-17T23:00Z" />
     <Resolution v="PT60M" />
     <Interval>
      <Pos v="1" />
      <Qty v="50935" />
     </Interval>
     <Interval>
      <Pos v="2" />
      <Qty v="48918" />
     </Interval>
     <Interval>
      <Pos v="3" />
      <Qty v="47347" />
     </Interval>
     <Interval>
      <Pos v="4" />
      <Qty v="46382" />
  </Interval>
 </Period>
</ScheduleTimeSeries>
</ScheduleMessage>

xml <- xmlInternalTreeParse(file = "test.xml")
xml_top <- xmlRoot(xml)
xml_children <- xmlChildren(x = xml_top)

但当我试图更深入地了解文件时：

xml_children2 <- xmlChildren(x = xml_children)

---

我还尝试使用

[]

或

[[]]

对文件进行子集划分，但这总是会导致我出现相同的错误。

使用XQuery处理器（如

xqilla

）时，这要简单得多：

$ echo 'for $v in //Qty/@v return xs:string($v)' | xqilla -i test.xml /dev/stdin
52452
50527
49221
49344
50935
48918
47347
46382

然后可以使用

read.table

轻松读入输出。您还可以使用该包在R中运行此操作，或如中所示

---

学分：到

我使用以下方法解决了我的问题：

xpathSApply(doc = xml_top, 
            file = "//ScheduleMessage/ScheduleTimeSeries/Period/Interval/Qty", 
            fun = xmlAttrs)

---

试试这个//Qty/@v

xpathSApply(doc = xml_top, 
            file = "//ScheduleMessage/ScheduleTimeSeries/Period/Interval/Qty", 
            fun = xmlAttrs)