[rrd-users] Negative graphs, absolute values

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Thu May 7 19:10:21 CEST 2009

----- Original Message ----- 
From: "Caio Brentano" <caiobrentano at gmail.com>
To: <rrd-users at lists.oetiker.ch>
Sent: Wednesday, May 06, 2009 8:59 PM
Subject: [rrd-users] Negative graphs, absolute values

> Hi all
> I need some help.
> I intend to plot charts with some DSs in "negative y-axis", such as 
> network
> traffic graphics where "IN" is plotted positive and "OUT" negative.
> I did some using '-' operator in CDEF definition, but I got a problem. My
> values under the graphic area are negatives, so when I got the MAX value 
> in
> the period, I got a wrong value. I need the absolute values.
> Do you have any example for me? I should use INF and NEGINF, shoudn't I?
> Thanks in advace.

Do everything like you would do when you plot it on the positive axis.
Use the original data to print, compare and what more.
Then have an extra CDEF which multiplies with -1.
Use that inverted data to graph.

If that does not work (please do share this on the list in that case!) then 
try using MIN instead of MAX.


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