title: How to read an XML input file, manipulate some nodes (remove and rename some) and write the output to a new XML output file?
body: <p>I need to read an XML file from internet and re-shape it.
  Here is the XML file and the code I have so far.</p>
  
  <pre><code>library(XML)
  url='http://ClinicalTrials.gov/show/NCT00001400?displayxml=true'  
  doc = xmlParse(url,useInternalNode=TRUE)
  </code></pre>
  
  <p>I was able to use some functions within the XML package with sucess(e.g., getNodeSet), but I am not an expert and there are some examples on the internet but I was not able to crack this problem myself. I also know some XPath but this was 4 years ago and I am not an expert on sapply and similar functions.</p>
  
  <p>But my goal is this:</p>
  
  <ol>
  <li><p>I need to remove a whole set of XML children branches about location, for example: <code>&lt;location&gt;  ... anything &lt;/location&gt;</code>.  There can be multiple nodes with location data. I simply don't need that detail in the output.  The XML file above always complies to an XSD schema. The root node is called <code>&lt;clinical_study&gt;</code>.</p></li>
  <li><p>The resulted simplified file should be written into a new XML file called "data-changed.xml".</p></li>
  <li><p>I also need to rename and move one branch from old nested place of </p>
  
  <p><code>&lt;eligibility&gt;
     &lt;criteria&gt;
       &lt;textblock&gt;
         Inclusion criteria are xyz
       &lt;/textblock/&gt;...</code></p></li>
  <li><p>In new output ("data-changed.xml") the structure should say a different XML node and be directly under root node: </p>
  
  <p><code>&lt;eligibility_criteria&gt; 
     Inclusion criteria are xyz
  &lt;/eligibility_criteria&gt;</code></p></li>
  </ol>
  
  <p>So I need to:</p>
  
  <ul>
  <li>read the XML into memory</li>
  <li>manipulate the tree (prune it somewhere)</li>
  <li>move some XML nodes to a new place and under a new name and </li>
  <li>write the resulting XML output file. </li>
  </ul>
  
  <p>Any ideas are greatly appreciated?</p>
  
  <p>Also, if you know about a nice (recent !) tutorial on XML parsing within R (or book chapter which tackles it, please share the reference). (I read the vignettes by Duncan and these are too advanced (too concise)). </p>