[rrd-users] Request for Enhancement (grapher)

[Owen DeLong]

I have a set of RRAs where I am gathering relatively high resolution
(.01 degree 5 second interval) temperature data.  In doing my analysis
of the data, I've found that the MIN and MAX consolidation functions
are quite useful over larger consolidation periods, while the AVERAGE
is very useful at high resolution.  I'd like to have the ability to
generate composite graphs which display the AVERAGE at one resolution
while simultaneously displaying the MIN/MAX at a much broader
consolidation.

It would be nice if the grapher could support something like:

DEF:min:temperature.rrd:MIN:3600
DEF:avg:temperature.rrd:AVERAGE
DEF:max:temperature.rrd:MAX:3600

Then, I could graph something like (background is black):

AREA:max#ff0000
AREA:min#000000
LINE3:avg#800000

This would give me the high resolution average superimposed as a line
over the stripe stretching from the hourly minimum to the hourly
maximum.
I can probably implement this, but I wanted to ask about the following
before I did so...

	1.	Has anyone already accomplished this so I don't have to?

	2.	Do enough people see value to this capability to make it
		worth changing the syntax so that this capability could
		get rolled into a future release if I do make it work?

	3.	Does anyone have a suggestion on a better way to implement
		the syntax.  I figured by making the :step optional at
		the end of the DEF, it would remain compatible with
		existing scripts, but also allow this flexibility.

Another enhancement I'm considering is modifying the RPN capabilities
to support PREV[variable] for retrieving the previous value of another
variable.  If anyone has any ideas or thoughts on the usefulness of
this, I'd like to hear them.

Finally, what do people think of having an RPN function called SUM
or SIGMA, which would be of the form:

	CDEF:foo=sourcevar,SUM

Which would result in foo containing a "Total to date" for each
iteration,
and would allow a GPRINT of foo MAX with "Total: %lf" to print a total
of the
data in sourcevar.

Thanks,

Owen

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