extract_clustering_data.xsl

<?xml version="1.0" encoding="UTF-8" ?>
<xsl:transform
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    version="3.0">

  <xsl:output method="text"/>
  
  <xsl:variable name="year-list" as="xs:string *">
    <xsl:for-each select="//tr">
      <xsl:value-of select="substring-before(substring-after(td[1],'gv/'),'_')" />
    </xsl:for-each>
  </xsl:variable>

  <xsl:variable name="all_refs" as="xs:string *">
    <xsl:for-each select="//tr">
      <xsl:value-of select="td[2]"/>
    </xsl:for-each>
  </xsl:variable>

  <xsl:template match="/">
    <xsl:variable name="dom" select="."/>
    <xsl:for-each select="distinct-values($year-list)">
      <xsl:sort data-type="number"  select="."/>
      <xsl:variable name="year" select="."/>
      "<xsl:value-of select="."/>"<xsl:text> </xsl:text>
      <xsl:variable name="rows" as="node() *">
        <xsl:for-each select="$dom//tr[contains(td[1],$year)]">
          <xsl:copy-of select="."/>
        </xsl:for-each>
      </xsl:variable>
 
      <xsl:for-each select="distinct-values($all_refs)">
        <xsl:variable name="ref" select="."/>

        <xsl:variable name="counter" as="xs:integer *">
          <xsl:for-each select="$rows//td[.=$ref]">1</xsl:for-each>
        </xsl:variable>
        <xsl:value-of select="sum($counter)"/><xsl:text> </xsl:text>

        </xsl:for-each><xsl:text>
      </xsl:text>
      
    </xsl:for-each>
  </xsl:template>
  
</xsl:transform>