Aggregate-function for sum and product in XPath
Solution 1
Use this XPath 2.0 expression:
sum(/items/item/(value * quantity))
Here is an XSLT 2.0 transformation as verification:
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:template match="/">
<xsl:sequence select="sum(/items/item/(value * quantity))"/>
</xsl:template>
</xsl:stylesheet>
When this transformation is applied on the provided XML document:
<items>
<item>
<value>1.0</value>
<quantity>3</quantity>
</item>
<item>
<value>2.5</value>
<quantity>2</quantity>
</item>
<!-- ... -->
</items>
the XPath expression is evaluated and the result of this evaluation is output:
8
Explanation:
In XPath 2.0 it is legal for a location step to be
/(expression)
,
or even
/someFunction(argumentList)
II. XSLT 1.0 solution:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:template match="/*">
<xsl:call-template name="sumProducts">
<xsl:with-param name="pNodes" select="item"/>
</xsl:call-template>
</xsl:template>
<xsl:template name="sumProducts">
<xsl:param name="pNodes" select="/.."/>
<xsl:param name="pAccum" select="0"/>
<xsl:choose>
<xsl:when test="not($pNodes)">
<xsl:value-of select="$pAccum"/>
</xsl:when>
<xsl:otherwise>
<xsl:call-template name="sumProducts">
<xsl:with-param name="pNodes" select="$pNodes[position() >1]"/>
<xsl:with-param name="pAccum" select=
"$pAccum + $pNodes[1]/value * $pNodes[1]/quantity"/>
</xsl:call-template>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
</xsl:stylesheet>
when this transformation is applied on the provided XML document (above), again the wanted, correct result is produced:
8
Do note: Such kind of problems are easy to solve using the FXSL library. The template to call is transform-and-sum
.
Solution 2
Try this:
<xsl:stylesheet version="2.0"xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:template match="/">
<xsl:sequence select="sum(/items/item/(value * quantity))"/>
</xsl:template>
</xsl:stylesheet>
Solution 3
Based on this suggestion https://stackoverflow.com/a/1334165/948404 I came up with a solution compliant with XSLT 1.0 and XPath 1.0, which are implemented by libxml/libxslt, used by PHPs implementation of XSLTProcessor
(thanks to @Dimitre Novatchev for confirmation).
<?xml version="1.0" encoding="UTF-8"?>
<xsl:transform version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/items">
<xsl:call-template name="recursivesum">
<xsl:with-param name="items" select="*" />
</xsl:call-template>
</xsl:template>
<xsl:template name="recursivesum">
<xsl:param name="items" />
<xsl:param name="sum" select="0" />
<xsl:variable name="head" select="$items[1]" />
<xsl:variable name="tail" select="$items[position()>1]" />
<xsl:variable name="thissum" select="$head/value * $head/quantity" />
<xsl:choose>
<xsl:when test="not($tail)">
<xsl:value-of select="$sum+$thissum" />
</xsl:when>
<xsl:otherwise>
<xsl:call-template name="recursivesum">
<xsl:with-param name="sum" select="$sum+$thissum" />
<xsl:with-param name="items" select="$tail" />
</xsl:call-template>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
</xsl:transform>
Comments
-
hielsnoppe almost 2 years
Similar to this question (http://stackoverflow.com/q/1333558/948404) I want to use XPath to calculate a sum over products in a structure like this:
<items> <item> <value>1.0</value> <quantity>3</quantity> </item> <item> <value>2.5</value> <quantity>2</quantity> </item> <!-- ... --> </items>
Is there an XPath expression that calculates the sum of the products of each items
value
andquantity
?Update: The solution has to work with PHPs XSLTProcessor class meaning that it probably has to be XSLT 1.0 compliant. This is why I did not yet accept the two probably correct answers using XSLT 2.0. I could neither test them in my PHP implementation nor in my browser nor in the Tryit Editor [1] from w3schools. Sorry!
-
hielsnoppe almost 12 yearsLooks promising to me, but can't get it to work with PHPs XSLTProcessor. Is this a problem of PHP or didn't I adapt it correctly?
-
web_bod almost 12 yearstrouble with writing things from memory
-
hielsnoppe almost 12 yearsLike I commented on the other answer this looks promising to me, but I can not get it to work with PHP. Is this a problem of PHP only supporting XSLT 1.0 / XPath 1.0, or did I not adapt it correctly? Is there a similar solution for version 1.0?
-
Dimitre Novatchev almost 12 years@hielsnoppe: AFAIK PHP uses libxml/libxslt, which only implements XPath 1.0 / XSLT 1.0. It is impossible to calculate the wanted value with a single XPath 1.0 expression only. If you are interested in an XSLT 1.0 solution, please, confirm, and I'll provide such.
-
hielsnoppe almost 12 yearsThank you for clarification on this! I now came up with a solution myself, posted as an answer.