[rrd-users] [GRAYMAIL] Re: Re: RE: RE: Question about trend line

rseiwert rob at vcaglobal.com
Fri Aug 14 02:40:12 CEST 2015

```Anything you can calculate you can draw. If you can define it as an equation you can put it in a cdef.
Of course it's going to take some thought, understanding RPN, and a little trial and error.
At this point you probably would be off using one graphs generated by vnstat.
Not knowing the exact nature of your data I cannot say exactly what you want. I
It seems you want to draw a line from 0,0 through the last point of your data, this is prediction I think vnstat uses.
I almost can see the solution but I don't want to work it out wrong here.
Something like (last value / secs in period of last value) * Step width then create a cdef that equals this value * count.
There may be a better way, if someone knows please enlighten me.

From: Ondrej [via RRD Mailinglists] [mailto:ml-node+s937164n7583094h65 at n2.nabble.com]
Sent: Thursday, August 13, 2015 4:28 PM
To: Robert C. Seiwert <rob at vcaglobal.com>
Subject: [GRAYMAIL] Re: Re: RE: RE: Question about trend line

I decided to have vnstat estimation line information in my graph and I am considering also to have LSL. in future i'll try to do some good combination.

but one more question. Is is possible to draw a skewed line in RRD? let say, the very beginning of the graph the line would start at zero and at the very end it would end at number that would reflect the trend. for users this quick look would give immediate awareness where there are, even the line would not perfectly copy true utilisation one.

i did not find the way how to draw skewed line.
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