xslt code choose between maximum of 2 values - xslt

Question

I have this xml file.
<?xml version="1.0" encoding="utf-8"?>
<racine>
<index>
<Parent nom="00000002" Name="" Address="" />
<Meter numSerie="00000002" />
<arrêté dateArrêté="28/02/2015 00:00:00">
<ValeurIndex Libelle="Val1">23.334</ValeurIndex>
<ValeurIndex Libelle="Val2">5.186</ValeurIndex>
<ValeurIndex Libelle="Val3">2.79</ValeurIndex>
</arrêté>
</index>
</racine>
and I would like to convert it in a txt file, where I need to add a new row with the value of max between Val1 and Val2, as the example below.
Val1,23.334
Val2,5.186
Val3,2.79
MaxVal1Vl2,23.334
What I created it was something like:
<xsl:choose>
<xsl:when test="#Libelle = 'Val1'">Val1</xsl:when>
<xsl:when test="#Libelle = 'Val2'">Val2</xsl:when>
<xsl:when test="#Libelle = 'Val3'">Val3</xsl:when>
</xsl:choose>
<xsl:text>,</xsl:text>
<xsl:value-of select="."/>
<xsl:text>
</xsl:text>
how can I add the 4 row being the max of Val1 and Val2?
Thanks

Answer 1

Try:
XSLT 1.0
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text" encoding="utf-8"/>
<xsl:template match="/racine">
<xsl:for-each select="index/arrêté/ValeurIndex">
<xsl:value-of select="#Libelle"/>
<xsl:text>,</xsl:text>
<xsl:value-of select="."/>
<xsl:text>
</xsl:text>
</xsl:for-each>
<xsl:variable name="v1" select="index/arrêté/ValeurIndex[#Libelle='Val1']" />
<xsl:variable name="v2" select="index/arrêté/ValeurIndex[#Libelle='Val2']" />
<xsl:text>MaxVal1Vl2,</xsl:text>
<xsl:choose>
<xsl:when test="$v1 > $v2">
<xsl:value-of select="$v1"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$v2"/>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
</xsl:stylesheet>