[rrd-users] Intermittent data causing stepped graphs

[jamiedg]

I've been using RRD for sometime to chart temp sensor data and have found it
to be one of the best charting tools , the charts generate in the blink of
an eye and use only minimal resources.
Recently though I've hit a problem that maybe someone can help with;
My temp sensors would normally save data at least once a min which worked
fine, but to extend battery life the newer sensors are only transmitting
data when the temp changes or at most every hour. This causes intermittent
data causing the charts to sometimes have a stepped output.

<http://rrd-mailinglists.937164.n2.nabble.com/file/n7583586/Temp_over_6h_RRD.jpg> 

When I post the same data to the cloud service EmonCMS I get a more smoothed
output.

<http://rrd-mailinglists.937164.n2.nabble.com/file/n7583586/Temp_over_6h_EmonCMS.jpg> 

Because the data could change every 30s, I have the step at 30 but the
heartbeat at 3600 and the xff at 20%

See the below rrd create script:

rrdtool create sen3step30.rrd \
--step 30 \
DS:Sen3:GAUGE:3600:U:U \
DS:Temp3:GAUGE:3600:U:U \
RRA:AVERAGE:0.2:1:1440 \
RRA:AVERAGE:0.2:6:1440 \
RRA:AVERAGE:0.2:36:1440 \
RRA:AVERAGE:0.2:144:1440 \
RRA:AVERAGE:0.2:1008:1440

I use the below chart script:
rrdtool graph /var/www/graphs/graph03t.png --start end-6h --height 150
--width 700 --end now --slope-mode --title "Temp for last 6h"
--vertical-label Temp --alt-autoscale-max    \
DEF:sen3=/home/pi/cc/sen3step30.rrd:Temp3:AVERAGE   
CDEF:cdefsen3=sen3,UN,PREV,sen3,1,*,IF   
LINE3:cdefsen3#9A2EFE:'Conservatory Temp'  \

If the data is Undefined I use the Prev value (sen3,UN,PREV,sen3,1,*,IF)

Can anyone please offer any suggestions or help to smooth the stepped graph
output.

rrdtool -v = RRDtool 1.4.7  

thanks and regards,
jamie



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