根据相关节点的属性和文本值解析XML [英] Parse XML based on attributes and text values of related nodes

问题描述

我之前用过XML包解析过HTML和XML，对xPath有初步的了解.然而，我被要求考虑 XML 数据，其中重要的位由元素本身的文本和属性以及相关节点中的属性组合确定.我从来没有这样做过.例如

I have used the XML package to parse both HTML and XML before, and have a rudimentary grasp of xPath. However I've been asked to consider XML data where the important bits are determined by a combination of text and attributes of the elements themselves, as well as those in related nodes. I've never done that. For example

[更新示例，稍微扩展]

[updated example, slightly more expansive]

<Catalogue>
<Bookstore id="ID910705541">
  <location>foo bar</location>
  <books>
    <book category="A" id="1">
        <title>Alpha</title>
        <author ref="1">Matthew</author>
        <author>Mark</author>
        <author>Luke</author>
        <author ref="2">John</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="B" id="10">
        <title>Beta</title>
        <author ref="1">Huey</author>
        <author>Duey</author>
        <author>Louie</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="D" id="100">
        <title>Gamma</title>
        <author ref="1">Tweedle Dee</author>
        <author ref="2">Tweedle Dum</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
  </books>
  </Bookstore> 
<Bookstore id="ID910700051">
  <location>foo</location>
  <books>
    <book category="A" id="1">
        <title>Happy</title>
        <author>Dopey</author>
        <author>Bashful</author>
        <author>Doc</author>
        <author ref="1">Grumpy</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="B" id="10">
        <title>Ni</title>
        <author ref="1">John</author>
        <author ref="2">Paul</author>
        <author ref="3">George</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="D" id="100">
        <title>San</title>
        <author ref="1">Ringo</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
  </books>
 </Bookstore> 
<Bookstore id="ID910715717">
    <location>bar</location>
  <books>
    <book category="A" id="1">
        <title>Un</title>
        <author ref="1">Winkin</author>
        <author>Blinkin</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="B" id="10">
        <title>Deux</title>
        <author>Nod</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="D" id="100">
        <title>Trois</title>
        <author>Manny</author>
        <author>Moe</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
  </books>
 </Bookstore> 
</Catalogue>

我想提取所有作者姓名，其中:1) location 元素有一个包含NY"的文本值2) author 元素不包含ref"属性；这就是作者标签中不存在 ref 的地方

I would like to extract all author names where: 1) the location element has a text value that contains "NY" 2) the author element does NOT contain a "ref" attribute; that is where ref is not present in the author tag

我最终需要在给定的书店内将提取的作者连接在一起，以便我的结果数据框是每个书店一行.我想在我的数据框中保留书店 ID 作为附加字段，以便我可以唯一地引用每个商店.由于只有第一家 bokstore 位于纽约，因此这个简单示例的结果类似于:

I will ultimately need to concatenate the extracted authors together within a given bookstore, so that my resulting data frame is one row per store. I'd like to preserve the bookstore id as an additional field in my data frame so that I can uniqely reference each store. Since only the first bokstore is in NY, results from this simple example would look something like:

1 Jane Smith John Doe Karl Pearson William Gosset

如果另一家书店在其位置包含NY"，它将包含第二行，依此类推.

If another bookstore contained "NY" in its location, it would comprise the second row, and so forth.

在这些复杂的条件下，我是否要求太多的 R 来解析?

Am I asking too much of R to parser under these convoluted conditions?

推荐答案

require(XML)

xdata <- xmlParse(apptext)
xpathSApply(xdata,'//*/location[text()[contains(.,"NY")]]/following-sibling::books/.//author[not(@ref)]')
#[[1]]
#<author>Jane Smith</author> 

#[[2]]
#<author>John Doe</author> 

#[[3]]
#<author>Karl Pearson</author> 

#[[4]]
#<author>William Gosset</author> 

细分:

获取所有包含NY"的位置

Get all locations containing 'NY'

//*/location[text()[contains(.,"NY")]]

获取这些节点的书籍兄弟

Get the books sibling of these nodes

/following-sibling::books

从这些注释中获取所有没有 ref 属性的作者

from these notes get all authors without a ref attribute

/.//author[not(@ref)]

如果需要文本，请使用 xmlValue:

Use xmlValue if you want the text:

> xpathSApply(xdata,'//*/location[text()[contains(.,"NY")]]/following-sibling::books/.//author[not(@ref)]',xmlValue)
[1] "Jane Smith"     "John Doe"       "Karl Pearson"   "William Gosset"

更新:

child.nodes <- xpathSApply(xdata,'//*/location[text()[contains(.,"NY")]]/following-sibling::books/.//author[not(@ref)]')

ans.func<-function(x){
    xpathSApply(x,'.//ancestor::bookstore[@id]/@id')
}

sapply(child.nodes,ans.func)
# id  id  id  id 
#"1" "1" "1" "1" 

更新 2:

使用更改后的数据

xdata <- '<Catalogue>
<Bookstore id="ID910705541">
  <location>foo bar</location>
  <books>
    <book category="A" id="1">
        <title>Alpha</title>
        <author ref="1">Matthew</author>
        <author>Mark</author>
        <author>Luke</author>
        <author ref="2">John</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="B" id="10">
        <title>Beta</title>
        <author ref="1">Huey</author>
        <author>Duey</author>
        <author>Louie</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="D" id="100">
        <title>Gamma</title>
        <author ref="1">Tweedle Dee</author>
        <author ref="2">Tweedle Dum</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
  </books>
  </Bookstore> 
<Bookstore id="ID910700051">
  <location>foo</location>
  <books>
    <book category="A" id="1">
        <title>Happy</title>
        <author>Dopey</author>
        <author>Bashful</author>
        <author>Doc</author>
        <author ref="1">Grumpy</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="B" id="10">
        <title>Ni</title>
        <author ref="1">John</author>
        <author ref="2">Paul</author>
        <author ref="3">George</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="D" id="100">
        <title>San</title>
        <author ref="1">Ringo</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
  </books>
 </Bookstore> 
<Bookstore id="ID910715717">
    <location>bar</location>
  <books>
    <book category="A" id="1">
        <title>Un</title>
        <author ref="1">Winkin</author>
        <author>Blinkin</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="B" id="10">
        <title>Deux</title>
        <author>Nod</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="D" id="100">
        <title>Trois</title>
        <author>Manny</author>
        <author>Moe</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
  </books>
 </Bookstore> 
</Catalogue>'

注意以前你有 bookstore 现在 Bookstore.NY 不见了，所以我用了 foo

Note previously you had bookstore now Bookstore. NY is gone so I have used foo

require(XML)
xdata <- xmlParse(xdata)
child.nodes <- getNodeSet(xdata,'//*/location[text()[contains(.,"foo")]]/following-sibling::books/.//author[not(@ref)]')

ans.func<-function(x){
  xpathSApply(x,'.//ancestor::Bookstore[@id]/@id')
}

sapply(child.nodes,ans.func)
#           id            id            id            id            id 
#"ID910705541" "ID910705541" "ID910705541" "ID910705541" "ID910700051" 
#           id            id 
#"ID910700051" "ID910700051"

xpathSApply(xdata,'//*/location[text()[contains(.,"foo")]]/following-sibling::books/.//author[not(@ref)]',xmlValue)
# [1] "Mark"    "Luke"    "Duey"    "Louie"   "Dopey"   "Bashful" "Doc"    

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