[rrd-developers] Re: [rrd-users] Next question: x,UN,0,IF funky output

Tobias Oetiker oetiker at ee.ethz.ch
Wed Aug 4 01:59:05 MEST 1999

Yesterday you sent me mail regarding [rrd-users] Next question:  x,UN,0,IF...:

*> Since I stack lots of data on top of each other, I use the following
*> CDEF to ensure that my data is either defined or zero:
*> 	CDEF:xdata=data,UN,0,data,IF,8,*
*> The problem with this is that my graphs turn out with the last point
*> always at zero.  This makes it look like my traffic is always diving
*> towards zero!
*> My hypothesis is that the .rrd archive returns an undefined value for
*> any time since the last update.  This makes sense in a pedantic sort
*> of way, but when I draw the graph and see the lines diving toward zero
*> at the far right, it doesn't make sense at all.
*> Is there a way to have it both ways?  I mean, have my graphs *not*
*> dive toward zero, but have undefined data interpreted as zero for
*> stacking purposes?

yes you could use the TIME and the NOW variable in your CDEF to have a time
dependant behavior ... 

on the developers list there has just been a discussion on the stacking of
*UNKNOWN* and it has been determined that stacking unknown should be treated
as if not stacking anything ... so you will not have to turn unknown into 0
anymore starting from 1.0.4 ...


*> Dave
*> --
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