[rrd-users] [unsure] Re: Things not adding up

Simon Hobson linux at thehobsons.co.uk
Fri Apr 8 21:18:09 CEST 2011

Long wrote:

>I also get avg(A) + avg(B) is not equal to avg(A+B). Can someone explain
>this too?

That's odd because it should work.

>Also, last(A) + last(B) is equal to last(A+B) for me. Will this always hold
>or I am just lucky that things add up nicely for me just for this case?

It should do provided "last" means the same in both databases. If the 
step value is the same, and both are updated near enough at the same 
time (or at least on or shortly after the end of each step period) 
then the time of "last(something)" should be the same. But if you 
last update was a second before the end of a step for one, and just 
after for the other, then last(something) would refer to different 
time periods until the old one got updated and the period could be 

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
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