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outlier

Description

This command is used to remove outlying numerical values, not to detect outlying values. The command removes or truncates outliers in the specified fields. If no fields are specified, the outlier command processes all fields.

Syntax

outlier <outlier-options> [<field-list>]

Optional arguments

<outlier-options>
Syntax: <action> | <mark> | <param> | <uselower>
Description: Outlier options. See "Descriptions for the outlier-options".
<field-list>
Syntax: <field> ...
Description: Comma or space-delimited list of field names.

Outlier-options

<action>
Syntax: action= remove | transform
Description: Specify what to do with the events with outlying numerical value. The remove option removes the event. The transform option truncates the outlying value to the threshold for outliers and, if mark=true, prefixes the value with "000".
Abbreviations: rm for remove, tf for transform.
Default: transform or tf
Syntax: mark=<bool>
Description: If action=transform, and mark=true, then prefix values pulled into the non-outlying range with "000". If action=remove, the mark option has no effect.
Default: false
<param>
Syntax: param=<num>
Description: Parameter controlling the threshold of outlier detection. An outlier is defined as a numerical value that is outside of the param threshold, multiplied by the inter-quartile range (IQR).
Default: 2.5
<uselower>
Syntax: uselower=<bool>
Description: Controls whether to look for outliers for values below the median in addition to above the median.
Default: false

Usage

Filtering is based on the inter-quartile range (IQR), which is computed from the difference between the 25th percentile and 75th percentile values of the numeric fields. If a field value in an event is less than (25th percentile) - param*IQR or greater than (75th percentile) + param*IQR , that field is transformed or that event is removed based on the action parameter.

Examples

1: Remove all outlying numerical values

... | outlier

2: For a timechart of web server events, transform the outlying average CPU values

Create a timechart of web server events of the average CPU seconds by host. Transform the outlying values of the host averages.

404 host="webserver" | timechart avg(cpu_seconds) by host | outlier action=tf

See also

anomalies, anomalousvalue, cluster, kmeans

Answers

Have questions? Visit Splunk Answers and see what questions and answers the Splunk community has using the outlier command.

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This documentation applies to the following versions of Splunk® Enterprise: 4.3, 4.3.1, 4.3.2, 4.3.3, 4.3.4, 4.3.5, 4.3.6, 4.3.7, 5.0, 5.0.1, 5.0.2, 5.0.3, 5.0.4, 5.0.5, 5.0.6, 5.0.7, 5.0.8, 5.0.9, 5.0.10, 5.0.11, 5.0.12, 5.0.13, 5.0.14, 5.0.15, 5.0.16, 5.0.17, 5.0.18, 6.0, 6.0.1, 6.0.2, 6.0.3, 6.0.4, 6.0.5, 6.0.6, 6.0.7, 6.0.8, 6.0.9, 6.0.10, 6.0.11, 6.0.12, 6.0.13, 6.0.14, 6.1, 6.1.1, 6.1.2, 6.1.3, 6.1.4, 6.1.5, 6.1.6, 6.1.7, 6.1.8, 6.1.9, 6.1.10, 6.1.11, 6.1.12, 6.1.13, 6.2.0, 6.2.1, 6.2.2, 6.2.3, 6.2.4, 6.2.5, 6.2.6, 6.2.7, 6.2.8, 6.2.9, 6.2.10, 6.2.11, 6.2.12, 6.2.13, 6.2.14


Comments

mark=true works with tabular results, but seems to have no effect when I chart the results.
Is there a way to mark outliers in charts?

Kutzi
February 12, 2015

Kbern, you're correct. the default is action=tf. I've corrected the docs. Thank you!

Sophy, Splunker
April 6, 2012

The documentation for "outlier" (above) says that "action", "Defaults to rm". That is not what I'm seeing in Splunk 4.2.3... I'm seeing it default to TF

Kbern
March 22, 2012

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