<xsl:variable name="lines" as="element()*">
      <xsl:analyze-string select="text()" regex="'">
        <xsl:non-matching-substring>
          <xsl:element name="line">
            <xsl:attribute name="length"
select="string-length(normalize-space(.))"/>
            <xsl:attribute name="text" select="."/>
          </xsl:element>
        </xsl:non-matching-substring>
      </xsl:analyze-string>
    </xsl:variable>

I can get the average like so including the last line

<xsl:variable name="averageLineLength"
          select="round(avg($lines/@length))" as="xs:double"/>

I can get the last line length without error

<xsl:variable name="averageLineLength"
          select="round(avg($lines[last()]/@length))" as="xs:double"/>

However in the case where my number lines is greater than 2 <xsl:when
test="$numberLines ge 2"> I don't want to include the last line as
part of my count and was trying the following

<xsl:variable name="averageLineLength"
          select="round(avg($lines[last()]/preceding-sibling::node()/@length))"
as="xs:double"/>

Which gives me the error:

Description: An empty sequence is not allowed as the value of variable
$averageSpaceNormalizedLineLength

	Martin Honnen
	http://msmvps.com/blogs/martin_honnen/