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diff --git a/web/api/queries/des/README.md b/web/api/queries/des/README.md deleted file mode 100644 index 0cc1a918e..000000000 --- a/web/api/queries/des/README.md +++ /dev/null @@ -1,77 +0,0 @@ -<!-- -title: "double exponential smoothing" -sidebar_label: "double exponential smoothing" -custom_edit_url: https://github.com/netdata/netdata/edit/master/web/api/queries/des/README.md -learn_status: "Published" -learn_topic_type: "References" -learn_rel_path: "Developers/Web/Api/Queries" ---> - -# double exponential smoothing - -Exponential smoothing is one of many window functions commonly applied to smooth data in signal -processing, acting as low-pass filters to remove high frequency noise. - -Simple exponential smoothing does not do well when there is a trend in the data. -In such situations, several methods were devised under the name "double exponential smoothing" -or "second-order exponential smoothing.", which is the recursive application of an exponential -filter twice, thus being termed "double exponential smoothing". - -In simple terms, this is like an average value, but more recent values are given more weight -and the trend of the values influences significantly the result. - -> **IMPORTANT** -> -> It is common for `des` to provide "average" values that far beyond the minimum or the maximum -> values found in the time-series. -> `des` estimates these values because of it takes into account the trend. - -This module implements the "Holt-Winters double exponential smoothing". - -Netdata automatically adjusts the weight (`alpha`) and the trend (`beta`) based on the number -of values processed, using the formula: - -``` -window = max(number of values, 15) -alpha = 2 / (window + 1) -beta = 2 / (window + 1) -``` - -You can change the fixed value `15` by setting in `netdata.conf`: - -``` -[web] - des max window = 15 -``` - -## how to use - -Use it in alerts like this: - -``` - alarm: my_alert - on: my_chart -lookup: des -1m unaligned of my_dimension - warn: $this > 1000 -``` - -`des` does not change the units. For example, if the chart units is `requests/sec`, the result -will be again expressed in the same units. - -It can also be used in APIs and badges as `&group=des` in the URL. - -## Examples - -Examining last 1 minute `successful` web server responses: - --  --  --  --  --  - -## References - -- <https://en.wikipedia.org/wiki/Exponential_smoothing>. - - |