xsl:sort: sorting by numeric value - xslt

Question

I have to sort out the codes in numerical order.
The codes have four characters and four numerals.
for example,
COMP2100
COMP2400
COMP3410
LAWS2202
LAWS2250
when I just do <xsl:sort select="code" order="ascending" />
it displays above result.
However, I want that to be in 'numerical order' that is
COMP2100
LAWS2202
COMP2250
COMP2400
COMP3410
How do I do this?

Answer 1

Note: the OP has now provided sample XML. The below theories can be trivially adapted to this XML.
I. XSLT 1.0 (part 1)
Here is a simple solution that assumes your assertion ("the codes have four characters and four numerals") will always be the case:
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:output omit-xml-declaration="no" indent="yes" />
<xsl:strip-space elements="*" />
<xsl:variable name="vNums" select="'1234567890'" />
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*" />
</xsl:copy>
</xsl:template>
<xsl:template match="/*">
<t>
<xsl:apply-templates>
<xsl:sort select="substring(., 5)"
data-type="number" />
</xsl:apply-templates>
</t>
</xsl:template>
</xsl:stylesheet>
...is applied to an imagined XML document, shuffled into random order:
<?xml version="1.0" encoding="utf-8"?>
<t>
<i>COMP3410</i>
<i>LAWS2202</i>
<i>COMP2400</i>
<i>COMP2100</i>
<i>LAWS2250</i>
</t>
...the correct result is produced:
<?xml version="1.0" encoding="utf-8"?>
<t>
<i>COMP2100</i>
<i>LAWS2202</i>
<i>LAWS2250</i>
<i>COMP2400</i>
<i>COMP3410</i>
</t>
Explanation:
The Identity Transform -- one of the (if not the) most fundamental design patterns in XSLT -- copies all nodes from the source XML document to the result XML document as-is.
One template overrides the Identity Transform by sorting all children of <t> based upon the characters in the string from position 5 to the string's end.
Again, note that this solution assumes your original assertion -- "the codes have four characters and four numerals" -- is (and always will be) true.
II. XSLT 1.0 (part 2)
A (potentially) safer solution would be to assume that there might be numerous non-numeric characters in various positions within the <i> nodes. In that case, this XSLT:
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:output omit-xml-declaration="no" indent="yes" />
<xsl:strip-space elements="*" />
<xsl:variable name="vNums" select="'1234567890'" />
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*" />
</xsl:copy>
</xsl:template>
<xsl:template match="/*">
<t>
<xsl:apply-templates>
<xsl:sort select="translate(., translate(., $vNums, ''), '')"
data-type="number" />
</xsl:apply-templates>
</t>
</xsl:template>
</xsl:stylesheet>
...provides the same result:
<?xml version="1.0" encoding="utf-8"?>
<t>
<i>COMP2100</i>
<i>LAWS2202</i>
<i>LAWS2250</i>
<i>COMP2400</i>
<i>COMP3410</i>
</t>
Explanation:
The Identity Transform is once again used.
In this case, the additional template uses the so-called Double Translate Method (first proposed by Michael Kay and first shown to me by Dimitre Novatchev) to remove all non-numeric characters from the value of each <i> element before sorting.
III. XSLT 2.0 Solution
Here's a possible XSLT 2.0 solution is very similar to part 2 of the XSLT 1.0 solution; it merely replaces the Double Translate Method with XPath 2.0's ability to handle regular expressions:
<xsl:sort select="replace(., '[^\d]', '')" data-type="number" />
Note that by no means are you required to use regular expressions in XPath 2.0; the Double Translate Method works just as well as in XPath 1.0. The replace() method will, however, most likely be more efficient.

Answer 2

There are two obvious errors in the provided XSLT code:
The namespace used to select elements is different from the default namespace of the provided XML document. Just change: xmlns:xsi="file://Volumes/xxxxxxx/Assignment" to xmlns:xsi="file://Volumes/xxxxxxx/Assignment".
The sort at present is not numeric. Change:
<xsl:sort select="xsi:code" order="ascending" />
to:
<xsl:sort select="substring(xsi:code, 5)" data-type="number" />
The complete transformation becomes:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:fn="http://www.w3.org/2005/xpath-functions"
xmlns:xsi="file://Volumes/u4783938/Assignment">
<xsl:template match="/">
<html>
<head>
<title> Course Catalogue </title>
</head>
<body bgcolor="#FF9999">
<h1> <div style="text-align:center"> Course Catalogue </div> </h1>
<xsl:for-each select="xsi:catalogue/xsi:course">
<xsl:sort select="substring(xsi:code, 5)"
data-type="number" />
<div style="width:1000px;margin-bottom:4px;color:white;background-color:#F36;text-align:justify;border:outset;margin-left:auto;margin-right:auto;">
<xsl:apply-templates select="xsi:code" />
<br />
<xsl:apply-templates select="xsi:title" />
<br />
<xsl:apply-templates select="xsi:year" />
<br />
<xsl:apply-templates select="xsi:science" />
<br />
<xsl:apply-templates select="xsi:area" />
<br />
<xsl:apply-templates select="xsi:subject" />
<br />
<xsl:apply-templates select="xsi:updated" />
<br />
<xsl:apply-templates select="xsi:unit" />
<br />
<xsl:apply-templates select="xsi:description" />
<br />
<xsl:apply-templates select="xsi:outcomes" />
<br />
<xsl:apply-templates select="xsi:incompatibility" />
</div>
</xsl:for-each>
</body>
</html>
</xsl:template>
</xsl:stylesheet>
and when applied on this XML document:
<catalogue xmlns="file://Volumes/u4783938/Assignment"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="file://Volumes/u4443554/Assignment/courses.xsd">
<course>
<code>ABCD3410</code>
<title> Information Technology in Electronic Commerce </title>
<year>later year</year>
<science>C</science>
<area> Research School of Computer Science </area>
<subject> Computer Science </subject>
<updated>2012-03-13T13:12:00</updated>
<unit>6</unit>
<description>Tce </description>
<outcomes>Up trCommerce. </outcomes>
<incompatibility>COMP1100</incompatibility>
</course>
<course>
<code>COMP2011</code>
<title> Course 2011 </title>
<year>Year 2011</year>
<science>C++</science>
<area> Research School of Computer Science </area>
<subject> Computer Science </subject>
<updated>2012-03-13T13:12:00</updated>
<unit>6</unit>
<description>Tce </description>
<outcomes>Up trCommerce. </outcomes>
<incompatibility>COMP1100</incompatibility>
</course>
</catalogue>
the produced result is now correctly sorted by the numeric part of the course code:
<html xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:fn="http://www.w3.org/2005/xpath-functions" xmlns:xsi="file://Volumes/u4783938/Assignment">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title> Course Catalogue </title>
</head>
<body bgcolor="#FF9999">
<h1>
<div style="text-align:center"> Course Catalogue </div>
</h1>
<div style="width:1000px;margin-bottom:4px;color:white;background-color:#F36;text-align:justify;border:outset;margin-left:auto;margin-right:auto;">COMP2011<br> Course 2011 <br>Year 2011<br>C++<br> Research School of Computer Science <br> Computer Science <br>2012-03-13T13:12:00<br>6<br>Tce <br>Up trCommerce. <br>COMP1100
</div>
<div style="width:1000px;margin-bottom:4px;color:white;background-color:#F36;text-align:justify;border:outset;margin-left:auto;margin-right:auto;">ABCD3410<br> Information Technology in Electronic Commerce <br>later year<br>C<br> Research School of Computer Science <br> Computer Science <br>2012-03-13T13:12:00<br>6<br>Tce <br>Up trCommerce. <br>COMP1100
</div>
</body>
</html>