RE: Statistics - Calculating Standard Deviation

> The performance is the thing that is worrying me most.  Ideally the
> target processor is MSXML 4.0, but that is open to negotiation...
 
Well using saxon 7.x (use the latest) and exslt/math you could use the following simple stylesheet.  Im just wondering how much of this can be done using straight xslt 2 now... Is there a square root function? I had a quick look but didn’t see anything.


<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
  	xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
 	xmlns:exsl="http://exslt.org/math">
 
<xsl:variable name="mean" select="sum(/root/node) div count(/root/node)"/>

<xsl:variable name="diffs">
  <root>
    <xsl:for-each select="/root/node">
      <node squaredDiff="{exsl:power($mean - .,2)}">
         <xsl:copy-of select="."/>
      </node>
    </xsl:for-each>
  </root>
</xsl:variable>

<xsl:variable name="mean.Of.Sum.Of.Diffs">
  <xsl:for-each select="$diffs">
    <xsl:value-of select="sum(/root/node/@squaredDiff) div (count (/root/node)-1)"/>
  </xsl:for-each>
</xsl:variable>
 
<xsl:template match="/">
  standard deviation: <xsl:value-of select="exsl:sqrt(number($mean.Of.Sum.Of.Diffs))"/>
</xsl:template>

</xsl:stylesheet>

Use on xml like:

<root>
  <node>1</node>
  ...
  <node>9</node>
  <node>10</node>
</root>

cheers
andrew

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