How it works...

The xmlParse function returns an object of the XMLInternalDocument class, which is a C-level internal data structure.

The xmlRoot() function gets access to the root node and its elements. Let us check the first element of the root node:

> rootNode[1] 
 
$CD 
<CD> 
  <TITLE>Empire Burlesque</TITLE> 
  <ARTIST>Bob Dylan</ARTIST> 
  <COUNTRY>USA</COUNTRY> 
  <COMPANY>Columbia</COMPANY> 
  <PRICE>10.90</PRICE> 
  <YEAR>1985</YEAR> 
</CD> 
attr(,"class") 
[1] "XMLInternalNodeList" "XMLNodeList" 

To extract data from the root node, we use the xmlSApply() function iteratively over all the children of the root node. The xmlSApply function returns a matrix.

To convert the preceding matrix into a data frame, we transpose the matrix using the t() function and then extract the first two rows from the cd.catalog data frame:

> cd.catalog[1:2,] 
             TITLE       ARTIST COUNTRY     COMPANY PRICE YEAR 
1 Empire Burlesque    Bob Dylan     USA    Columbia 10.90 1985 
2  Hide your heart Bonnie Tyler      UK CBS Records  9.90 1988