[rrd-developers] Re: rrdgraph question

Per Jessen per at computer.org
Thu Jul 28 19:43:33 MEST 2005

Ruud H.G. van Tol wrote:

> Suppose you have a DS:n:COUNTER, and a CDEF:hot that is either 0 (<=24)
> or 1 (>24), maybe you can make a CDEF:nhot that is average(hot)*(n-PREV(n))?

Thanks Ruud. 

It wasn't quite the answer, but it got me on to the right track.  

I'm recording temperature as DS:temp:GAUGE and refrigeration as DS:refrig:GAUGE.  The
"refrig" datasource is a binary 0 or 1, indicating refrigeration off or on.  

To display average day temperature and duration of refrigeration: 

"DEF:temp=rrd:S3D7C:AVERAGE "
"DEF:refrig=rrd:refrig:AVERAGE "
"CDEF:d88=refrig,24,* " 
"LINE2:temp#0000FF:\"Outside temperature\" "
"LINE2:d88#ff0000:\"Refrigeration on-time\" "

I'll most likely not need to display this with any other resolution than 24 hour or
greater, but regardless I think I'm now left with getting the step-size into my CDEF


This shows (1) the average daily temperature and 2) the amount of time the refrigeration
plant was on-line.  The latter has a fixed energy-consumption, so effectively the graph
shows also the amount of energy used for refrigeration. 

/Per Jessen, Zürich

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