Explanation about DEF entry in graph

[li0n]

Hi,

i have two data source: mem_free and mem_total. and i want to calculate the data "used memory" on the graph with all consolidation AVG/LAST/MAX/MIN (and hide mem_total of course)

i've tried to make a graph and a CDEF:
debug graph:
DEF:a="/opt/lampp/htdocs/cacti/rra/prafwadm01_mem_total_444.rrd":mem_total:AVERAGE
DEF:b="/opt/lampp/htdocs/cacti/rra/prafwadm01_mem_free_443.rrd":mem_free:AVERAGE

my question is: how a and b are chosen ? because i need to create the CDEF:
CDEF:cdefa=a,b,- \

at this time, it's ok for AVG but i did not find how to create other DEF for mem_total:LAST MIN and MAX

is there any documentation about how Graph Template Items and graph item input are linked together in cacti algorithm ? (unsuccesfull search on this forum)
can i use the same CDEF for LAST/MAX/MIN calculation ? what is the purpose of the tick boxes in Associated Graph Items ?

thx !

[rony]

Pretty much the order that the items are on the graph will get the DEF assigned alpha wise.