[rrd-users] Fixing holes in my graph

Frank Pineau frank at pineaus.com
Thu Jan 4 00:24:36 MET 2001

Nothing really important that needs fixing.  I generate some graphs based on
temperature and windspeed METAR information that I retrieve from NOAA every
fifteen minutes.  Unfortunately, due to things like network outages, etc, the
update occasionally fails and I end up with big fat blank spaces in my graph
where NAN's were entered into the database.  I thought for awhile I would just
leave them there to show when the network was unavailable, but now they just
look ugly.

My thought is to go ahead and draw the blanks until it updates successfully,
then somehow take the reading just before the outage and the reading just after
the outage and interpolate those back into the hole in the database.  For
example, if the temperature was 30,32,30,30,NAN,NAN,33,36 take the NAN's and
replace them with 31 and 32, respectively.  Alternatively, simply say "If you
get a NAN, use the last known good value instead" (this would be less
desireable, but still better than a hole in the graph). 

The problem is I can't even begin to guess at how to do something like that.
Anyone care to take a crack at it?  Is it even possible?


Frank Pineau  ------------>

        frank at pineaus.IHATESPAM.com

 Give me liberty or give me something of equal or
  lesser value from your glossy 32-page catalog.
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