[drraw-users] Unable to graph with VDEF operators LSLSLOPE, LSLINT, and LSLCORREL

[David Nolan]

On 7/19/07, Nokes, Sam X <nokess at upmc.edu> wrote
>
> Realizing v2.2a3 is beta, and noting a comment by Alex: "In RRDtool 1.2 I
> made a start with VDEF processing. VDEFs aren't arrays like CDEFs are, they
> are single values. The work is far from finished, however certain functions
> are already usable."( http://www.vandenbogaerdt.nl/rrdtool/total.php ),
> the questions follow:
> (1) Are the VDEF operators LSLSLOPE, LSLINT, and LSLCORREL usable in drraw
> v2.2a3?
> (2) Should the vnames be placed into a linear equation:
> y=LSLSLOPE*LSLCORREL+LSLINT ?
>    We tried to add a CDEF definition substituting VDEF vnames in a vpn
> format (D,F,*,H,+) and
>    received an error from drraw stating "rpn expressions without DEF or
> CDEF variables are not supported"
> (3) Has anyone generated a least squares projection with rrdtool similar
> to the following? If so what is the rrd invocation?
>

Sam,

I've never used these functions in rrdtool before, but my reading of the
documentation indicates that you are close with statement 2 above.
I believe you need to define the VDEF variables as you're doing, and then
define a CDEF using those variables and the automatic
COUNT variable, i.e. CDEF:trend=D,COUNT,*,H,+  (using the variables you
defined above), and then graph the CDEF.

-David
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