how to find the highest value using xsl - html

Question

i would like to find the highest temperate of the month APRIL, the xml has other month too.
how can i code in my xsl to retrieve the highest temperate?
here is my XML code
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="THISISA3.xsl"?>
<forecast qTime="28/10/20 10:00 PM" qLocation="Singapore">
<weather yyyymmdd="20200430">
<year>2020</year>
<month>04</month>
<date>30</date>
<comment>Plenty of sunshine</comment>
<code>sunny</code>
<highest>32.6</highest>
<lowest>28.4</lowest>
</weather>
<weather yyyymmdd="20200421">
<year>2020</year>
<month>04</month>
<date>21</date>
<comment>Plenty of sunshine</comment>
<code>sunny</code>
<highest>32.2</highest>
<lowest>29.8</lowest>
</weather>
</forecast>

Answer 1

It is good to provide the required output and also to show the efforts made to get the result as the community here to help with specific problems and not to write the whole code.
However, if you're newbie to start with xslt then below code with comments could help you to get started and to understand the use of stuff in xslt.
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:output method="xml" indent="yes"/>
<xsl:strip-space elements="*"/>
<!-- key is used to identify nodes within an expression -->
<xsl:key name="highTemp" match="highest" use="."/>
<!-- identity template to result the transformation in source XML doc itself -->
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<!-- matching a root node -->
<xsl:template match="forecast">
<!-- iterating through each 'weather' element -->
<xsl:for-each select="weather">
<!-- selecting node which matches the variable having required highest temperature -->
<xsl:apply-templates select=".[highest=$monthApril]"/>
</xsl:for-each>
</xsl:template>
<xsl:variable name="monthApril">
<!-- iterate only 'weather' elements which are from month of April -->
<xsl:for-each select="//weather[substring(#yyyymmdd,5,2) = '04']">
<!-- sorting in descending order so that node having highest temp comes first -->
<xsl:sort select="key('highTemp', highest)" order="descending"/>
<xsl:if test="position()=1">
<xsl:value-of select="highest"/>
</xsl:if>
</xsl:for-each>
</xsl:variable>
</xsl:stylesheet>

Answer 2

It would be nice if you specified what the required output is and how the variables are set and which version of xslt you use.
Below is an example XSLT 1.0 template (it has name 'highestTempForMonth') with the ability to specify the required month (it can be specified in a parameter 'month' for template) and with the ability to call this template with required month in any place you want to do it.
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0" >
<xsl:output method="xml" indent="yes" encoding="Utf-8"/>
<xsl:variable name="requiredMonth" select="'04'"/>
<xsl:template match="/">
<HighestTemperature>
<value>
<xsl:call-template name="highestTempForMonth">
<xsl:with-param name="month" select="$requiredMonth"/>
</xsl:call-template>
</value>
</HighestTemperature>
</xsl:template>
<xsl:template name="highestTempForMonth">
<xsl:param name="month"/>
<xsl:for-each select="/forecast/weather[month = $month]/highest">
<xsl:sort select="." data-type="number" order="descending"/>
<xsl:if test="position() = 1"><xsl:value-of select="."/></xsl:if>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
There is XSLT 2.0 equivalent (with a little bit simpler template part) example.
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="#all" version="2.0" >
<xsl:output method="xml" indent="yes" encoding="Utf-8"/>
<xsl:variable name="requiredMonth" select="'04'"/>
<xsl:template match="/">
<HighestTemperature>
<value>
<xsl:call-template name="highestTempForMonth">
<xsl:with-param name="month" select="$requiredMonth"/>
</xsl:call-template>
</value>
</HighestTemperature>
</xsl:template>
<xsl:template name="highestTempForMonth">
<xsl:param name="month"/>
<xsl:value-of select="max(/forecast/weather[month = $month]/highest/xs:double(.))"/>
</xsl:template>
</xsl:stylesheet>
For both examples if there are no values for the specified month, the 'value' tag with an empty value will be specified. This value can be changed by a simple condition if necessary.