[rrd-users] Re: rolling average

[Serge Maandag]

> Is it possible to have a weighted average like eg. 0.5 val[t]+0.3
> val[t-1]+0.2 val[t-2] ?

Kind of, I use (val[t-1] - val[t]) * 0.93 + val[t].

I think I stole it from this list once.
By changing the weight factor 0.93, you can change how slow the line
responds.

Together with some catching of exceptions, it becomes something like:

DEF:val=/rrd/bla/..
CDEF:avg=PREV,UN,val,UN,1,val,IF,PREV,IF,val,UN,1,val,IF,-,0.93,*,val,UN
,1,val,IF,+
LINE1:val
LINE1:avg

So PREV has been replaced with:
IF (PREV=UN) {
	val
} else {
	PREV
}

and val has been replaced with:

IF (val==UN){
	1
} else {
	val
}

Serge.

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