CDEF for averaging multiple data-sources

[jfbus]

It would be nice to have the ability to have graphs like this one :

Graph Item #1 : DS#1 (LINE1, no color)
Graph Item #2 : DS#2 (LINE1, no color)
Graph Item #3 : DS#3 (LINE1, no color)
Graph Item #4 : CDEF AVERAGE_PREVIOUS (LINE2, color)
Graph Item #5 : DS#4 (LINE1, no color)
Graph Item #6 : DS#5 (LINE1, no color)
Graph Item #7 : DS#6 (LINE1, no color)
Graph Item #8 : CDEF AVERAGE_PREVIOUS (LINE2, color)

Graph Item #4 displays the average of DS#1, DS#2, DS#3.
Graph Item #8 displays the average of DS#4, DS#5, DS#6.

I just created a patch to add this CDEF :
http://forums.cacti.net/viewtopic.php?t=10090&start=0