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[[search-aggregations-metrics-extendedstats-aggregation]]
=== Extended Stats
A `multi-value` metrics aggregation that computes stats over numeric values extracted from the aggregated documents. These values can be extracted either from specific numeric fields in the documents, or be generated by a provided script.
The `extended_stats` aggregations is an extended version of the <<search-aggregations-metrics-stats-aggregation,`stats`>> aggregation, where additional metrics are added such as `sum_of_squares`, `variance` and `std_deviation`.
Assuming the data consists of documents representing exams grades (between 0 and 100) of students
[source,js]
--------------------------------------------------
{
"aggs" : {
"grades_stats" : { "extended_stats" : { "field" : "grade" } }
}
}
--------------------------------------------------
The above aggregation computes the grades statistics over all documents. The aggregation type is `extended_stats` and the `field` setting defines the numeric field of the documents the stats will be computed on. The above will return the following:
[source,js]
--------------------------------------------------
{
...
"aggregations": {
"grades_stats": {
"count": 6,
"min": 72,
"max": 117.6,
"avg": 94.2,
"sum": 565.2,
"sum_of_squares": 54551.51999999999,
"variance": 218.2799999999976,
"std_deviation": 14.774302013969987
}
}
}
--------------------------------------------------
The name of the aggregation (`grades_stats` above) also serves as the key by which the aggreagtion result can be retrieved from the returned response.
==== Script
Computing the grades stats based on a script:
[source,js]
--------------------------------------------------
{
...,
"aggs" : {
"grades_stats" : { "extended_stats" : { "script" : "doc['grade'].value" } }
}
}
--------------------------------------------------
===== Value Script
It turned out that the exam was way above the level of the students and a grade correction needs to be applied. We can use value script to get the new stats:
[source,js]
--------------------------------------------------
{
"aggs" : {
...
"aggs" : {
"grades_stats" : {
"extended_stats" : {
"field" : "grade",
"script" : "_value * correction",
"params" : {
"correction" : 1.2
}
}
}
}
}
}
--------------------------------------------------
|
