# [rrd-users] question for an "average counter" rrd

Matthias Lemke m at box.li
Sat Feb 23 15:32:33 CET 2013

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On 23.02.2013 15:14, Alex van den Bogaerdt wrote:
>> I habe a pellet oven with webinterface (austrian ETA). The webinterface
>> works perfect. I can read and set most of the values.
>>
>> Two of the values are counter:
>> - pelles in kg
>> - working time in seconds
>>
>> I put the pellets in kg in a counter rrd. So I can see for instance
>> pellets/day vs. outside temperature.
>
> Internally RRDtool will compute and store the number of kilograms per
> second.
>

Yes right, I multiply with 86400 ...

>> Now I am interested in the value of pellets per year. My imagination
>> would be a gliding yearly average (every day the rrd will be updatet
>> with the pellets of the last 365 days).
>
> Don't update like this. Just keep updating the RRD as usual.

I do this since more than a year.

> Then display 365 days in a graph of 365 pixels wide.
>
> Each pixel column will show the average number of kilograms per second
> during that day.

right.

>
> If you print the average of those 365 values in your graph, you have the
> average number of kilograms per day measured over an entire year.

puh, how can I do this?

>
> A year is 365 times 24 times 60 times 60 seconds. That is 31536000 seconds.
> Just multiply the rate you already have in your RRD by 31536000, and then
> compute the average. The outcome will be the number of kilograms during the
> past 365 days, which is the sliding window you want.

Here I need also a hint or help how I can do this...

>
> One small problem is that for RRDtool a day starts and ends at midnight UTC,
> which is close but not equal to your time. I don't think this should be
> relevant, even if you would live at the other side of the globe.

not relevant, right.

>
> The other small problem is that you count kilograms, not pellets. This you
> could solve by another multiplication in your CDEF, number of pellets per
> kilogram.

my fault, I am interested furhtermore in kg of pellets.
counting pellets is on the way to counting sand :)

thanks and regards

>
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