[rrd-users] Adding two VDEF values together

[Yannick Marquet]

Hello,
>> So, a VDEF is a set of data and a CDEF is a single value, but a TOTAL
>> will be a single value?
no, it is opposite :
http://oss.oetiker.ch/rrdtool/doc/rrdgraph_data.en.html#IVDEF
http://oss.oetiker.ch/rrdtool/doc/rrdgraph_data.en.html#ICDEF

CDEF and DEF, are series of values, number of value depends on step 
parameter an the consolidation function (/CF/).
VDEF is a single value.

You cant use CDEF without DEF or CDEF variables because you can't 
calculate number of value needed for series.

Le 21/02/2013 22:37, Alex van den Bogaerdt a écrit :
>> I was trying to do something which I thought was fairly simple, but I
>> keep on getting the following error:
>>
>> "ERROR: rpn expressions without DEF or CDEF variables are not supported"
>>
>> In the most simplest form, I am trying to do the following:
>>
>> DEF:A=<rrdfile>:A:AVERAGE
>> DEF:B=<rrdfile>:B:AVERAGE
>>
>> VDEF:TA=A,TOTAL
>> VDEF:TB=B,TOTAL
>>
>> CDEF:TAB=TA,TB,ADDNAN
>>
>> So, a VDEF is a set of data and a CDEF is a single value, but a TOTAL
>> will be a single value?
> VDEF support is currently very limited. What you are trying to do is,
> indeed, not possible this way.
>
>> I am trying to take two totals and add them together - seems fairly
>> common to want to do this?
> The workaround is to do your math inside a CDEF, and then find the total.
>
> CDEF:c=a,b,ADDNAN
> VDEF:total=c,TOTAL
>
> hth
> alex
>
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