[rrd-users] How to find first valid dp in rrd - repost - where arethe experts?

Simon Hobson linux at thehobsons.co.uk
Wed Nov 19 21:29:37 CET 2008

Just tossing an idea up in the air - it either flies or gets shot 
down ! Bear with me, I'm off with flu at the moment so not thinking 

Could you do a cdef along the lines of :

t=if (prev(t) is unknown AND d is not unknown) then t=time(d) else t=unknown.

This should, if I'm switched on enough, work through the data, and 
set t to the timestamp of the first sample where the data is unknown. 
For the initial data both prev(t) and d will be unknown and so t will 
stay as unknown. Once the data is known, then prev(t) will cease to 
be unknown and no further updates will happen.

That's assuming the functions required are available - I'll leave 
someone else to work that out.
Simon Hobson

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