First read up about standard grouping techniques such as Muenchian grouping
at http://www.jenitennison.com/xslt/grouping

Computing a subtotal for each group is then a minor variant of the
technique: instead of merely iterating over the items in the group using
xsl:for-each, you can assign the node-set comprising the group to a
variable, and then sum over that using the sum() function.

Like all grouping problems, it's much easier in 2.0:

<xsl:for-each-group select="rows" group-by="columnA">
  <xsl:apply-templates select="current-group()"/>
  <subtotal><xsl:value-of select="sum(current-group()/columnB)"/></subtotal>
</xsl:for-each-group>

Michael Kay
http://www.saxonica.com/ 

> -----Original Message-----
> From: dsk [mailto:dmitrik@xxxxxxxxxxxxxx] 
> Sent: 05 January 2005 04:09
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject:  for-each and summing based on group
> 
> 
> within a for-each there might be various sets of values which 
> produce the 
> following grid, where val is equal to a number
> 
> a  val val val
> a  val val val
> a  val val val
> b  val val val
> b  val val val
> c  val val val
> c  val val val
> 
> what is the best way to insert a sum line for the first
> column a, one for b, and one for c.
> 
> is a nested for each needed? or checking to see if the 
> following value is 
> not equal to the preceding, then then summing?
> 
> thanks,
> Dmitri
> 
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