[[ml-metric-functions]]
=== Metric Functions

The metric functions include functions such as mean, min and max. These values
are calculated for each bucket. Field values that cannot be converted to
double precision floating point numbers are ignored.

The {xpackml} features include the following metric functions:

* <<ml-metric-min,`min`>>
* <<ml-metric-max,`max`>>
* <<ml-metric-median,`median`>>
* <<ml-metric-high-median,`high_median`>>
* <<ml-metric-low-median,`low_median`>>
* <<ml-metric-mean,`mean`>>
* <<ml-metric-high-mean,`high_mean`>>
* <<ml-metric-low-mean,`low_mean`>>
* <<ml-metric-metric,`metric`>>
* <<ml-metric-varp,`varp`>>
* <<ml-metric-high-varp,`high_varp`>>
* <<ml-metric-low-varp,`low_varp`>>

[float]
[[ml-metric-min]]
==== Min

The `min` function detects anomalies in the arithmetic minimum of a value.
The minimum value is calculated for each bucket.

High- and low-sided functions are not applicable.

This function supports the following properties:

* `field_name` (required)
* `by_field_name` (optional)
* `over_field_name` (optional)
* `partition_field_name` (optional)
* `summary_count_field_name` (optional)

For more information about those properties,
see <<ml-detectorconfig,Detector Configuration Objects>>.

For example, if you use the following function in a detector in your job,
it detects where the smallest transaction is lower than previously observed.
You can use this function to detect items for sale at unintentionally low
prices due to data entry mistakes. It models the minimum amount for each
product over time.
//Detect when the minumum amount for a product is unusually low compared to its past amounts

[source,js]
--------------------------------------------------
{
  "function" : "min",
  "field_name" : "amt",
  "by_field_name" : "product"
}
--------------------------------------------------


[float]
[[ml-metric-max]]
==== Max

The `max` function detects anomalies in the arithmetic maximum of a value.
The maximum value is calculated for each bucket.

High- and low-sided functions are not applicable.

This function supports the following properties:

* `field_name` (required)
* `by_field_name` (optional)
* `over_field_name` (optional)
* `partition_field_name` (optional)
* `summary_count_field_name` (optional)

For more information about those properties,
see <<ml-detectorconfig,Detector Configuration Objects>>.

For example, if you use the following function in a detector in your job,
it detects where the longest `responsetime` is longer than previously observed.
You can use this function to detect applications that have `responsetime`
values that are unusually lengthy. It models the maximum `responsetime` for
each application over time and detects when the longest `responsetime` is
unusually long compared to previous applications.

[source,js]
--------------------------------------------------
{
  "function" : "max",
  "field_name" : "responsetime",
  "by_field_name" : "application"
}
--------------------------------------------------

This analysis can be performed alongside `high_mean` functions by
application. By combining detectors and using the same influencer this would
detect both unusually long individual response times and average response times
for each bucket. For example:

[source,js]
--------------------------------------------------
{
  "function" : "max",
  "field_name" : "responsetime",
  "by_field_name" : "application"
},
{
  "function" : "high_mean",
  "field_name" : "responsetime",
  "by_field_name" : "application"
}
--------------------------------------------------

[float]
[[ml-metric-median]]
==== Median

The `median` function detects anomalies in the statistical median of a value.
The median value is calculated for each bucket.

This function supports the following properties:

* `field_name` (required)
* `by_field_name` (optional)
* `over_field_name` (optional)
* `partition_field_name` (optional)
* `summary_count_field_name` (optional)

For more information about those properties,
see <<ml-detectorconfig,Detector Configuration Objects>>.

For example, if you use the following function in a detector in your job,
it models the median `responsetime` for each application over time. It detects
when the median `responsetime` is unusual compared to previous `responsetime`
values.

[source,js]
--------------------------------------------------
{
  "function" : "median",
  "field_name" : "responsetime",
  "by_field_name" : "application"
}
--------------------------------------------------

[float]
[[ml-metric-high-median]]
==== High_median

The `high_median` function detects anomalies in the statistical median of a value.
The median value is calculated for each bucket.
Use this function if you want to monitor unusually high median values.

This function supports the following properties:

* `field_name` (required)
* `by_field_name` (optional)
* `over_field_name` (optional)
* `partition_field_name` (optional)
* `summary_count_field_name` (optional)

For more information about those properties,
see <<ml-detectorconfig,Detector Configuration Objects>>.

[float]
[[ml-metric-low-median]]
==== Low_median

The `low_median` function detects anomalies in the statistical median of a value.
The median value is calculated for each bucket.
Use this function if you are just interested in unusually low median values.

This function supports the following properties:

* `field_name` (required)
* `by_field_name` (optional)
* `over_field_name` (optional)
* `partition_field_name` (optional)
* `summary_count_field_name` (optional)

For more information about those properties,
see <<ml-detectorconfig,Detector Configuration Objects>>.


[float]
[[ml-metric-mean]]
==== Mean

The `mean` function detects anomalies in the arithmetic mean of a value.
The mean value is calculated for each bucket.

This function supports the following properties:

* `field_name` (required)
* `by_field_name` (optional)
* `over_field_name` (optional)
* `partition_field_name` (optional)
* `summary_count_field_name` (optional)

For more information about those properties,
see <<ml-detectorconfig,Detector Configuration Objects>>.

For example, if you use the following function in a detector in your job,
it models the mean `responsetime` for each application over time. It detects
when the mean `responsetime` is unusual compared to previous `responsetime`
values.

[source,js]
--------------------------------------------------
{
  "function" : "mean",
  "field_name" : "responsetime",
  "by_field_name" : "application"
}
--------------------------------------------------

[float]
[[ml-metric-high-mean]]
==== High_mean

The `high_mean` function detects anomalies in the arithmetic mean of a value.
The mean value is calculated for each bucket.
Use this function if you want to monitor unusually high average values.

This function supports the following properties:

* `field_name` (required)
* `by_field_name` (optional)
* `over_field_name` (optional)
* `partition_field_name` (optional)
* `summary_count_field_name` (optional)

For more information about those properties,
see <<ml-detectorconfig,Detector Configuration Objects>>.

For example, if you use the following function in a detector in your job,
it models the mean `responsetime` for each application over time. It detects
when the mean `responsetime` is unusually high compared to previous
`responsetime` values.

[source,js]
--------------------------------------------------
{
  "function" : "high_mean",
  "field_name" : "responsetime",
  "by_field_name" : "application"
}
--------------------------------------------------

[float]
[[ml-metric-low-mean]]
==== Low_mean

The `low_mean` function detects anomalies in the arithmetic mean of a value.
The mean value is calculated for each bucket.
Use this function if you are just interested in unusually low average values.

This function supports the following properties:

* `field_name` (required)
* `by_field_name` (optional)
* `over_field_name` (optional)
* `partition_field_name` (optional)
* `summary_count_field_name` (optional)

For more information about those properties,
see <<ml-detectorconfig,Detector Configuration Objects>>.

For example, if you use the following function in a detector in your job,
it models the mean `responsetime` for each application over time. It detects
when the mean `responsetime` is unusually low
compared to previous `responsetime` values.

[source,js]
--------------------------------------------------
{
  "function" : "low_mean",
  "field_name" : "responsetime",
  "by_field_name" : "application"
}
--------------------------------------------------

[float]
[[ml-metric-metric]]
==== Metric

The `metric` function combines `min`, `max`, and `mean` functions. You can use
it as a shorthand for a combined analysis. If you do not specify a function in
a detector, this is the default function.
//TBD: Is that default behavior still true?

High- and low-sided functions are not applicable. You cannot use this function
when a `summary_count_field_name` is specified.

This function supports the following properties:

* `field_name` (required)
* `by_field_name` (optional)
* `over_field_name` (optional)
* `partition_field_name` (optional)

For more information about those properties,
see <<ml-detectorconfig,Detector Configuration Objects>>.

For example, if you use the following function in a detector in your job,
it models the mean, min, and max `responsetime` for each application over time.
It detects when the mean, min, or max `responsetime` is unusual compared to
previous `responsetime` values.

[source,js]
--------------------------------------------------
{
  "function" : "metric",
  "field_name" : "responsetime",
  "by_field_name" : "application"
}
--------------------------------------------------


[float]
[[ml-metric-varp]]
==== Varp

The `varp` function detects anomalies in the variance of a value which is a
measure of the variability and spread in the data.

This function supports the following properties:

* `field_name` (required)
* `by_field_name` (optional)
* `over_field_name` (optional)
* `partition_field_name` (optional)
* `summary_count_field_name` (optional)

For more information about those properties,
see <<ml-detectorconfig,Detector Configuration Objects>>.

For example, if you use the following function in a detector in your job,
it models models the variance in values of `responsetime` for each application
over time. It detects when the variance in `responsetime` is unusual compared
to past application behavior.

[source,js]
--------------------------------------------------
{
  "function" : "varp",
  "field_name" : "responsetime",
  "by_field_name" : "application"
}
--------------------------------------------------

[float]
[[ml-metric-high-varp]]
==== High_varp

The `high_varp` function detects anomalies in the variance of a value which is a
measure of the variability and spread in the data. Use this function if you want
to monitor unusually high variance.

This function supports the following properties:

* `field_name` (required)
* `by_field_name` (optional)
* `over_field_name` (optional)
* `partition_field_name` (optional)
* `summary_count_field_name` (optional)

For more information about those properties,
see <<ml-detectorconfig,Detector Configuration Objects>>.

For example, if you use the following function in a detector in your job,
it models models the variance in values of `responsetime` for each application
over time. It detects when the variance in `responsetime` is unusual compared
to past application behavior.

[source,js]
--------------------------------------------------
{
  "function" : "high_varp",
  "field_name" : "responsetime",
  "by_field_name" : "application"
}
--------------------------------------------------


[float]
[[ml-metric-low-varp]]
==== Low_varp

The `low_varp` function detects anomalies in the variance of a value which is a
measure of the variability and spread in the data. Use this function if you are
just interested in unusually low variance.

This function supports the following properties:

* `field_name` (required)
* `by_field_name` (optional)
* `over_field_name` (optional)
* `partition_field_name` (optional)
* `summary_count_field_name` (optional)

For more information about those properties,
see <<ml-detectorconfig,Detector Configuration Objects>>.

For example, if you use the following function in a detector in your job,
it models models the variance in values of `responsetime` for each application
over time. It detects when the variance in `responsetime` is unusual compared
to past application behavior.

[source,js]
--------------------------------------------------
{
  "function" : "low_varp",
  "field_name" : "responsetime",
  "by_field_name" : "application"
}
--------------------------------------------------