Calculate an average per time base

BelgianViking · Post by **BelgianViking** » Thu Nov 16, 2006 1:41 am

I'm trying to define a CDEF that calculates an average increase of a graph item per time basis, but I can't seem to solve this. Mind you, this is completely different from the average function which is 'built-in'.
As an example, I have a graph showing the total number of pages printed on a certain printer. I would like to print the number of pages printed per day (hour, week, ... maybe). In this example this value should be calculated as (161308-159672)/32 days = 54,5 pages/day. So I need the minimum and maximum value of the selected time period and the lenght of the selected period in the graph to calculate this value.
I have searched the forums, but apparently, this has never been done before. Maybe it is not even possible ... ?
Thanks in advance !

africanw · Post by **africanw** » Thu Nov 16, 2006 1:47 am

Just do the Calcs before it gets to Cacti.

So if you are gathering the data via a script do it there then just put the results on the datasource and then into the graph.

BelgianViking · Post by **BelgianViking** » Thu Nov 16, 2006 2:36 am

I don't immediately see how I can do that ...
Suppose I get the value of the value of the total number of pages printed, and this value is 161431 pages; how can I calculate an average number of pages over the last hour, last day, last week from that value only ?
I also would like to have this average printed for whichever period selected in the graph.

Post by **gandalf** » Thu Nov 16, 2006 12:43 pm

See http://www.cacti.net/downloads/docs/htm ... _VARIABLES for some "statistic functions" of cacti
Reinhard

Post by **rony** » Thu Nov 16, 2006 12:46 pm

Well, if you had made this data source a COUNTER instead of a GAUGE, you would be seeing the data you would like to see.

BelgianViking · Post by **BelgianViking** » Fri Nov 17, 2006 2:20 am

If I make it a counter, I loose the total number of pages printed, don't I ? I agree that that would make it easy to calculate the number of pages printed in a certain period of time.

BelgianViking · Post by **BelgianViking** » Fri Nov 17, 2006 2:23 am

Maybe I could live with just the number of pages printed in the period that is displayed in the graph. This would be 'easy', I thought: just take the current (or max) value and subtract the MIN value. However, I don't seem to be able to do that in a CDEF. This can't be true, can it ?

Post by **gandalf** » Sun Nov 19, 2006 6:49 am

BelgianViking wrote:If I make it a counter, I loose the total number of pages printed, don't I ? I agree that that would make it easy to calculate the number of pages printed in a certain period of time.

That was already solved by a "nasty" workaround: Store both types, GAUGE _and_ COUNTER. Use two rrd's with one ds each or one rrd with two ds (this will require a wrapper script that prints the same data twice). Then use COUNTER for increments and GAUGE for absolute numbers
Reinhard

Calculate an average per time base

Calculate an average per time base

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