XPath with regex match on an attribute value

I’m trying to get the total number of
event nodes that contain the text ‘
doubles ‘ in the value of the
description attribute.

matches() is a standard XPath 2.0 function. It is not available in XPath 1.0.

You can use:

count(/*/*/event[contains(@description, ' doubles ')])

To verify this, here is a small XSLT transformation which just outputs the result of evaluating the above XPath expression on the provided XML document:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output method="text"/>


 <xsl:template match="https://stackoverflow.com/">
  <xsl:value-of select=
  "count(/*/*/event[contains(@description, ' doubles ')])"/>
 </xsl:template>
</xsl:stylesheet>

when this transformation is applied on the provided XML document:

<game id="2009/05/02/arimlb-milmlb-1" pk="244539">
    <team id="109" name="Arizona" home_team="false">
        <event number="9" inning="1" description="Felipe Lopez doubles to left fielder Chris Duffy.  "/>
        <event number="15" inning="1" description="Augie Ojeda flies out to center fielder Mike Cameron.  "/>
        <event number="23" inning="1" description="Chad Tracy doubles to right fielder Joe Sanchez.  "/>
        <event number="52" inning="2" description="Mark Reynolds lines out to left fielder Chris Duffy.  "/>
        <!-- more data here -->
    </team>
</game>

the wanted, correct result is produced:

2