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diff --git a/web/api/queries/ses/README.md b/web/api/queries/ses/README.md new file mode 100644 index 000000000..b5dacea83 --- /dev/null +++ b/web/api/queries/ses/README.md @@ -0,0 +1,54 @@ +# Single (or Simple) Exponential Smoothing (`ses`) + +> This query is also available as `ema` and `ewma`. + +An exponential moving average (`ema`), also known as an exponentially weighted moving average (`ewma`) +is a first-order infinite impulse response filter that applies weighting factors which decrease +exponentially. The weighting for each older datum decreases exponentially, never reaching zero. + +In simple terms, this is like an average value, but more recent values are given more weight. + +Netdata automatically adjusts the weight (`alpha`) based on the number of values processed, +using the formula: + +``` +window = max(number of values, 15) +alpha = 2 / (window + 1) +``` + +You can change the fixed value `15` by setting in `netdata.conf`: + +``` +[web] + ses max window = 15 +``` + +## how to use + +Use it in alarms like this: + +``` + alarm: my_alarm + on: my_chart +lookup: ses -1m unaligned of my_dimension + warn: $this > 1000 +``` + +`ses` does not change the units. For example, if the chart units is `requests/sec`, the exponential +moving average will be again expressed in the same units. + +It can also be used in APIs and badges as `&group=ses` in the URL. + +## Examples + +Examining last 1 minute `successful` web server responses: + +-  +-  +-  +-  + +## References + +- [https://en.wikipedia.org/wiki/Moving_average#exponential-moving-average](https://en.wikipedia.org/wiki/Moving_average#exponential-moving-average) +- [https://en.wikipedia.org/wiki/Exponential_smoothing](https://en.wikipedia.org/wiki/Exponential_smoothing). |