[rrd-users] Inserted value becomes NaN

Jon August jonaugust at gmail.com
Fri Jan 16 22:36:32 CET 2015

Got it.

Thanks for the clarification.


> On Jan 15, 2015, at 12:12 PM, Simon Hobson <linux at thehobsons.co.uk> wrote:
> Jon August <jonaugust at gmail.com> wrote:
>> I do an update like this:
>> rrdtool updatev filename.rrd N:1102
>> What am I doing wrong?
> One update does not create a value in the database - it merely sets a "known point", and for the very first update, all data up to that point is unknown. You need to make repeated updates over a period of time. Once you pass the *END* of a data point, then a value will be computed for the previous interval - but only if enough data has been entered for the interval to have a valid value, that's what the "fudge factor" (0.5 in your example) is for.
> So in your case, you need multiple updates, not more than 48 hours apart (or the data becomes unknown again), and after the end of a day* you will get a value if you have enough data to fill the previous 12 hours (0.5 x 1day) with valid data.
> * Note that a day will start/end at midnight UTC. All intervals end at an integer multiple of "step" after midnight Jan 1 1970 (unix epoch).
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