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POparsing xml to list in R: how to consistently access nodes when xml structure varies?
 

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    <h2>Background</h2> <p>I have a xml settings file that can look like this:</p> <pre><code>&lt;level1&gt; &lt;level2&gt; &lt;level3&gt; &lt;level4name&gt;bob&lt;/level4name&gt; &lt;/level3&gt; &lt;/level2&gt; &lt;/level1&gt; </code></pre> <p>but there can be multiple instances of <code>level3</code></p> <pre><code>&lt;level1&gt; &lt;level2&gt; &lt;level3&gt; &lt;level4name&gt;bob&lt;/level4name&gt; &lt;/level3&gt; &lt;level3&gt; &lt;level4name&gt;jack&lt;/level4name&gt; &lt;/level3&gt; &lt;level3&gt; &lt;level4name&gt;jill&lt;/level4name&gt; &lt;/level3&gt; &lt;/level2&gt; &lt;/level1&gt; </code></pre> <p>there can also be multiple types of <code>level4</code> nodes for each <code>level3</code>:</p> <pre><code> &lt;level3&gt; &lt;level4name&gt;bob&lt;/level4name&gt; &lt;level4dir&gt;/home/bob/ &lt;/level4dir&gt; &lt;level4logical&gt;TRUE&lt;/level4logical&gt; &lt;/level3&gt; </code></pre> <p>In R, I load this file using</p> <pre><code>settings.xml &lt;- xmlTreeParse(settings.file) settings &lt;- xmlToList(settings.xml) </code></pre> <p>I want to write a script that converts all of the values contained in <code>level4type1</code> to a vector of the unique values at this level, but I am stumped trying to do this in a way that works for all of the above cases.</p> <p>One of the problems is that the <code>class(settings[['level2']])</code> is a list for the first two cases and a matrix for the third case.</p> <pre><code>&gt; xmlToList(xmlTreeParse('case1.xml')) $level2.level3.level4name [1] "bob" &gt; xmlToList(xmlTreeParse('case2.xml')) level2 level3.level4name "bob" level3.level4name "jack" level3.level4name "jill" &gt; xmlToList(xmlTreeParse('case3.xml')) level2 level3 List,3 level3 List,1 level3 List,1 </code></pre> <h2>Questions</h2> <p>I have two questions:</p> <ol> <li><p>how can I extract a vector of the unique values of 'level4type1`</p></li> <li><p>is there a better way to do this? </p></li> </ol>
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