Sum of Multiplied Values

Question

I have a fairly convoluted XML file and I need to do a weighted average of a few values within it using XSL. I am able to complete a sum of the weights OR of the values, but I c

Answer 1

To follow the example in that question you linked to, you would use this in XSLT 2.0/XPath 2.0:

<xsl:variable name="FoosToCalculate"
              select="/group/fooList/foo[attributeList/Attribute/@ID = $test_id]" />
<xsl:variable name="WeightedVolume" 
              select="sum($FoosToCalculate/(attributeList/Attribute/@Weight * 
                                 Properties/PhysicalProperties/Volume/@Average)
                          )"/>

Doing this summing in XSLT 1.0 is considerably more involved and typically involves either using recursive templates or some manifestation of the node-set() function. Here is an example of the latter:

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

  <xsl:template match="/">
    <!-- determine $test_id however you need to -->
    <xsl:variable name="products">
      <xsl:for-each 
           select="/group/fooList/foo[attributeList/Attribute/@ID = $test_id]">
        <product>
          <xsl:value-of select="attributeList/Attribute/@Weight * 
                                Properties/PhysicalProperties/Volume/@Average" />
        </product>
      </xsl:for-each>
    </xsl:variable>

    <xsl:value-of select="sum(ex:node-set($products)/product)"/>
  </xsl:template>

</xsl:stylesheet>

Answer 2

For completeness, if you want to sum over a computed quantity in XSLT 1.0, there are three ways of doing it:

(a) recursion: write a recursive template that processes the items in the sequence one by one, computing the total as it goes.

(b) create an XML tree in which the computed quantities are node values, and then process this tree using the sum() function. To do this in a single stylesheet you will need the exslt:node-set() extension function.

(c) use an extension function provided by the XSLT vendor, or user-written using the facilities provided by the vendor for calling external functions.

In XSLT 2.0, it can always be done using the construct

sum(for $x in node-set return f($x))

where f is a function that computes the quantity.