[rrd-users] RRDs::graph and DEF... MIN

[Simon Hobson]

Joachim Hartmann <joachim.hartmann at gmx-topmail.de> wrote:

> Hi,
> I am monitoring my heating by a raspberry-pi using rrd data base:
> - TMP_V = flow temperature
> - TMP_R = return temperature
> - WOHNZ = indoor temperature
> - AUSEN = outdoor temperature
> - PUMPE = circulating pump (running or not)
...

> All looks fine as lpng as the outdoor temperatrure is above 0 degree.
> Otherwise the pump graph ends at the O line, it looks ugly!
> 
> My idea: drawing first something like this:
> ################################################################
>  ...
>  "DEF:Off=/home/pi/heizung.rrd:ausen:MIN",
>  "AREA:Off#F0EFEF",
>  "LINE1:Off#424242:",
>  ...
> ################################################################
> 
> but - my - RRDs::graph does not exept the line
> "DEF:Off=/home/pi/heizung.rrd:ausen:MIN",
> !!
> 
> Anyone an idea?

How about running through an RRD Graph once, but rather than drawing anything, use PRINT (NOT GPRINT) to get the minimum value of ausen and then you have a value (Perl variable) you can use as a constant in a second RRD Graph run.

So use VDEF to get the min value, then do some maths (further CDEFs) to draw the pumpe value between this min value and 1


> Sorry English is not my native language and school is long ago

No need to apologise, your English is a lot better than my German from school (also a lot of years ago) !