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authorDaniel Baumann <daniel.baumann@progress-linux.org>2018-11-07 12:19:29 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2018-11-07 12:20:17 +0000
commita64a253794ac64cb40befee54db53bde17dd0d49 (patch)
treec1024acc5f6e508814b944d99f112259bb28b1be /web/api/queries/median/README.md
parentNew upstream version 1.10.0+dfsg (diff)
downloadnetdata-upstream/1.11.0+dfsg.tar.xz
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New upstream version 1.11.0+dfsgupstream/1.11.0+dfsg
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+# Median
+
+The median is the value separating the higher half from the lower half of a data sample
+(a population or a probability distribution). For a data set, it may be thought of as the
+"middle" value.
+
+`median` is not an accurate average. However, it eliminates all spikes, by sorting
+all the values in a period, and selecting the value in the middle of the sorted array.
+
+## how to use
+
+Use it in alarms like this:
+
+```
+ alarm: my_alarm
+ on: my_chart
+lookup: median -1m unaligned of my_dimension
+ warn: $this > 1000
+```
+
+`median` 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=median` in the URL.
+
+## Examples
+
+Examining last 1 minute `successful` web server responses:
+
+- ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=min&after=-60&label=min)
+- ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=average&after=-60&label=average)
+- ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=median&after=-60&label=median&value_color=orange)
+- ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=max&after=-60&label=max)
+
+## References
+
+- [https://en.wikipedia.org/wiki/Median](https://en.wikipedia.org/wiki/Median).