[rrd-users] rrd graph inter/extrapolation of large U / NaN blocks

Joachim Larsson joachim.larsson at ericsson.com
Wed Feb 27 14:49:02 CET 2013


Im web-scraping a stock-market page which is only open daytime, thus my rrd-database will have huge gaps in the data. I've been trying to make a CDEF that uses old values and tries to inter/extrapolate the gaps, but to no avail.

Can anyone shed some light regarding converting U to a straight line between the previous and last successful rrd data?

I create the rrd with the following;
rrdtool create stocklol.rrd --start $starttime -s 300\
DS:latest:GAUGE:600:0:U \
DS:volume:COUNTER:600:0:U \
RRA:AVERAGE:0.5:1:8640 \

The data is being updated 0800 -> 1800 CET, all other values are NAN / U

Google and other sources doesnt hint on this, as far as i could tell. Alot of refrences to making unknown into 0, but that's absolutely not what i want. I checked the CDEF and RPN docs refrenced in rrdgraph pages.


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