[rrd-users] Re: SUM with RPN ?

[Alex van den Bogaerdt]

l.johnson wrote:
> 
> Hi everybody,
> just trying to "simply" sum values 
> eg)
> tot =0
> tot= tot+ value at time t
> tot = tot + value at time t+1  and so on 
> 
> seems so easy, but no result with that kind of code:
> ...
> DEF:val=$RRDFILE:val:MAX
> CDEF:tot1=tot,PREV,UN,0,tot,IF              // not sure for the syntax, anyway .. always incorrect ! 
> CDEF:tot= tot1,val,+
> ...
> 
> in other words , did anybody test the use of PREV or PREV(vname) as described in the rrdgraph manual or http://people.ee.ethz.ch/~oetiker/webtools/rrdtool/tutorial/cdeftutorial.html

???

If this example is in the tutorial, it is wrong.  I most certainly
didn't put it in there.

There's no relation whatsoever between PREV(tot1) and tot.

Anyway:

If "average" is "total/time"  then "total" is "average * time".

No need for complicated PREV statements.

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