Need help in performing +/- operations on selected TOTALS

[firstblock1]

Hi,
I have created aggregate graph using cacti and customized per my requirements. I need help in displaying two important values.

1. I need to perform summation of two specific totals (cache1 Total and cache2 Total). If I use |sum:auto:total:3:auto|, its going to add all the totals. I don't want to add all totals. I just want to add and display Cache 1 and Cache 2 totals.

2. Need to perform following calculations and display it on the same graph:
(INTERNET Total + CACHE Total) - (TO CLIENT Total).

Please see the attached image to get an idea. Is this achievable ?

Thank you,

[TheWitness]

I would think a cdef would do this quite well

[firstblock1]

How can I use CDEFs to perform required calculations on selected TOTALS...?

If so, can you please guide me.. Thanks

attaching RRDTool commands for this graph..

[TheWitness]

I see now. Let me forward to the guru....

[rony]

Graph variables do no support the use of CDEF as the data sources.

Now, there might be a way to use VDEF to perform the calculations you are trying to do. But, not sure if work around to use a VDEF in 0.8.7.

[firstblock1]

Thank you Tony,

I'll see if I can achieve my objectives using VDEF.
Will report back shortly.

Thanks.

[gandalf]

VDEFs are still not (officially) supported by cacti 087.
They are part of main trunk since about 2 years (or more?).
Once I had a patch to add that feature, but it's quite likely that it won't match the way we solved it in main trunk.
R.