[rrd-users] problem with plotting unkown data

[Bernd Kuhlen]

Hi,
I want to plot the number of processes on my server, defining fewer  
than 80 as ok, 80-120 as critical and more than 120 as overload.
Here's how I try to plot it:

/usr/local/bin/rrdtool graph /path/to/png/myserver.proc-6h.png -- 
start -21600 \
-t "myserver (6h number of processes, 5min intervals)" \
--lower-limit 0 \
--vertical-label "number of processes" \
DEF:nproc=/path/to/rrd/database/myserver.proc.rrd:nproc:AVERAGE \
"CDEF:newproc=nproc" \
CDEF:ok=newproc,$PROCCRITS,GT,$PROCCRITS,newproc,IF \
CDEF:many=newproc,$PROCCRITS,GT,newproc,$PROCCRITS,-,0,IF \
CDEF:over=newproc,$PROCCRITH,GT,newproc,$PROCCRITH,-,0,IF \
AREA:ok#0000FF:"ok" \
STACK:many#FFFF00:"critical" \
STACK:over#FF0000:"overload"

where PROCCRITS=80, PROCCRITH=120

for my actual monitored data it works fine. For processes < 80 I habe  
nice blue , for 80<=proc<=120 i have orange and red for more than 120  
proccesses.  The problem is that all unkown data (the time period  
that hasn't been monitored since I start at -21600 seconds i.e. 6  
hours in the past) is now displayed with 80 proccesses instead of 0.  
So all my plots start with a long blue constant 80 bar until the  
first point where the monitoring starts.

How can I avoid unkown data being treated as 80 proccesses and avoid  
the blue bar?

greets,
Bernd