Re: [rrd-users] Confusion about VDEF total and graph values

[Alex van den Bogaerdt]

> Actually talking about microcubes of gas per hour sounds kinda cool.

That's not what you show in your graph. You show microcubes of gas per
second, at a resolution of one hour.

It's easy enough to change that: just use a CDEF to multiply by 3600. Each
bar will then show the amount per hour.

It is easy to confuse yourself or the occasional other viewer when doing
so, so be careful.  For instance: you should get the VDEF from the
original DEF, not from the CDEF. Or else you would appear to use 3k6 times
the gas you are really using.


By the way: you may want to write down the number from the meter, do the
same 24 hours later, and compare against the graph. If it matches: good.
If not, you need to do some more bug hunting.  Perhaps you already think
of this, perhaps not.



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Re: [rrd-users] Confusion about VDEF total and graph values

[Simon Hobson]

humke  wrote:

> By the way, I am not sure why you don't see the code with the variables.
> It's there when I lookup the post via the forum solution on oetiker's
> rrdtool website:

Same here - I see it on the website, but not in the emails I got from the list. 
My guess is that it got stripped in the plain-text conversion by the mailing 
list manager.

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Re: [rrd-users] Confusion about VDEF total and graph values

[humke]

Actually talking about microcubes of gas per hour sounds kinda cool.

By the way, I am not sure why you don't see the code with the variables.
It's there when I lookup the post via the forum solution on oetiker's
rrdtool website:

[image: Inline image 1]



Groet,
Arjan

On Thu, Oct 13, 2016 at 4:06 PM, humke [via RRD Mailinglists] <
ml-node+s937164n7583427...@n2.nabble.com> wrote:

> Ah yes of course, that just explains it Alex, thanks!
>
> I didn't think this through enough. There's more happening than just
> calculating the difference between the last two measured values. When
> graphed that difference is spread out over 3600 seconds (in my case), thus
> indeed becoming a rate.
>
> I remember reading many times about this rate vs value thing (maybe even
> on your site). I guess working with GAUGE DST's a lot (which are already a
> rate) before starting with the gas counter made me forget this important
> part.
>
> Thanks again!
>
> --
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image.png (36K) 





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Re: [rrd-users] Confusion about VDEF total and graph values

[humke]

Ah yes of course, that just explains it Alex, thanks!

I didn't think this through enough. There's more happening than just
calculating the difference between the last two measured values. When
graphed that difference is spread out over 3600 seconds (in my case), thus
indeed becoming a rate. 

I remember reading many times about this rate vs value thing (maybe even on
your site). I guess working with GAUGE DST's a lot (which are already a
rate) before starting with the gas counter made me forget this important
part.

Thanks again!



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[rrd-users] Confusion about VDEF total and graph values

[humke]

Hi,

I am using rrdtool to store values from my smart meter (electricity and
gas). For the gas part I am a bit confused about what is graphed and shown
as a total for the graph's period of time. 

First, some info about the rrd file I use to store the gas counter values
from my meter:



Here's the code I use to create a graph from this rrd:



The $ variables are defined somewhere else and represent actual color codes
and the rrd file name. 

Here's an example of generated graph:

 

I was expecting the total value mentioned below the graph to be equal to the
sum of all values in the graph. But as you can see it is not (or I
misinterpret things). The gas counter value uses 3 decimal places and this
counter is in m3 (in the rrdinfo output you only see two decimals because
the last decimal is 0). I would expect the y-axis values to be represented
in 'm' instead of 'u'. When I add all the graph values myself I get to a
total of aprox. 380u m3. This does not match with the presented total of
1.384 m3. 

Likely I am misunderstanding some rrdtool concepts here. Could someone
enlighten me?

Humke



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