Calculations of Delta Time in the graphs

[lexxfirecore]

Hi,

I was playing a lot with CDEF functions in order to create delta time calculations,
the result was using a constant in formula instead time variable:
cdef=CURRENT_DATA_SOURCE,PREV(CURRENT_DATA_SOURCE),-,ABS,300,/
using constant 300 that represents polling time interval in second.


Would be great to have Delta and Delta Time calculations as cacti default CDEF functions or at least
to have a time interval variable that will be linked with graphs RRAs and would work in this kind of formulas.

P.S. If anyone knows how to create delta time using current configurations please help.