用 R 将 XML 的特定节点转换为 CSV

Question

I have XML file structured like this

<Item>
    <Tab1>
        <Info1>x<Info1>
        <Info2>y<Info2>
        <Info3>z<Info3>
    </Tab1>
    <Tab2>
        <Info1>foo<Info1>
        <Info2>bar<Info2>
        <Info3>foobar<Info3>
    </Tab2>
</Item>
<Item>
    <Tab1>
        <Info1>x<Info1>
        <Info2>y<Info2>
        <Info3>z<Info3>
    </Tab1>
    <Tab2>
        <Info1>foo<Info1>
        <Info2>bar<Info2>
        <Info3>foobar<Info3>
    </Tab2>
</Item>

Using this code

file <- "file.xml"
doc <- xmlParse(file, useInternalNodes = TRUE) 
xmldataframe <- xmlToDataFrame(doc)

I get dataframe that looks like this

Tab1              Tab2
xyz               foobarfoobar

But I need only Tab2 info in separate columns. How can I get the following result?

Info1 Info2 Info3
foo   bar   foobar

Answer 1

You need to fix up your example XML first (it is currently invalid), but given that you have a vaild XML document, you can use xpath to pull out specific nodes. You are usng the XML package it seems (helpful to specify this in a question) so the function XML::getNodeSet is what you need:

file <- "file.xml"
doc <- XML::xmlParse(file, useInternalNodes = TRUE)
tab2 <- XML::getNodeSet(doc, "//Tab2")
xmldataframe <- XML::xmlToDataFrame(tab2)

This gives only the nodes you are looking for.

> xmldataframe
  Info1 Info2  Info3
1   foo   bar foobar
2   foo   bar foobar