[rrd-users] Working with linear slope calculations

Alex van den Bogaerdt alex at ergens.op.het.net
Tue Jan 22 23:45:48 CET 2008

On Tue, Jan 22, 2008 at 09:51:27PM +0000, Simon Hobson wrote:
> Alex van den Bogaerdt wrote:
> >  > That's the bit I'm trying to avoid.  It seems like I have to hardcode
> >>  the size of the graph within a calculation.  That makes changing things
> >>  significantly more complex.  From your suggestion, I take it there's no
> >>  way to poll for those values directly?
> >
> >With a bit of programming, VDEF could support this.
> >It may not be the most efficient approach, but it will do.
> You mean, make some variables available (like environment variables 
> in the shell etc) with the various parameters used in the program 
> call ?

I was thinking about something similarly to:


Instead of working on DEFs or CDEFs, such functions could work on
internals of RRDtool, such as:


Giving it a bit more thought, I think that it may be better to skip
the VDEF step, and directly do: 


(where WIDTH and TOTALTIME are, from RPN's point of view, constants)

or to expand VDEF capabilities, so that it can do:


I still stand by my suggestion to discuss this on rrd-developers

Alex van den Bogaerdt

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