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How to take derivative of a sum of series

Asked by Jens Rantil

I have a couple of series of monotonically increasing values as a function of time. In other words, counters. I would like to graph the (non-negative) derivative of the sum of these series. Can I do that?

So far I have tried:

sumSeries(nonNegativeDerivative(my.series.*.count))

and

nonNegativeDerivative(sumSeries(my.series.*.count))

Neither of these works. Am I using the wrong functions? Can this be done?

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Jens Rantil
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Denis Zhdanov (deniszhdanov) said : 		#1

Hi Jens,

Usually you are need to use sumSeries(nonNegativeDerivative()) instead of vice versa - but main reason behind it is spikes - see http://www.jilles.net/perma/2013/08/22/how-to-do-graphite-derivatives-correctly/ for details. If you have no gaps in graphs both of them will work fine.

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Jens Rantil (jens-rantil) said : 		#2

Good call. I had non-continuous data that made the derivate break. Will see if correcting my retention policies can help here...