Question

If I have an XMLNode object that looks like this:

<foo>
 <a>1</a>
 <b>
  <c>1</c>
  <d>2</d>
 </b>
</foo>

(available as dput dump: https://gist.github.com/4273470)

without knowing the nestedness of the “c” node, how can I change its value from “1” to “2”? I have been playing with the XML package, but it is not terribly clear – most examples appear to deal with extracting rather than updating information.

I have also tried using xmlToList, but then I don’t know how to identify / update a node on a list of arbitrary depth either.

Answer 1

Here’s a two-step method. (test is the dput output you included).

Find the path to $c

> xmlApply(test,names)
$a
  text 
"text" 

$b
  c   d 
"c" "d" 

Replace $c once you know the path

xmlChildren(test[["b"]][["c"]]) <- "2"