[[search-aggregations-pipeline-avg-bucket-aggregation]]
=== Avg Bucket Aggregation

experimental[]

A sibling pipeline aggregation which calculates the (mean) average value of a specified metric in a sibling aggregation.
The specified metric must be numeric and the sibling aggregation must be a multi-bucket aggregation.

==== Syntax

An `avg_bucket` aggregation looks like this in isolation:

[source,js]
--------------------------------------------------
{
    "avg_bucket": {
        "buckets_path": "the_sum"
    }
}
--------------------------------------------------

.`avg_bucket` Parameters
|===
|Parameter Name |Description |Required |Default Value
|`buckets_path` |The path to the buckets we wish to find the average for (see <<buckets-path-syntax>> for more
 details) |Required |
 |`gap_policy` |The policy to apply when gaps are found in the data (see <<gap-policy>> for more
 details) |Optional |`skip`
 |`format` |format to apply to the output value of this aggregation |Optional | `null`
|===

The following snippet calculates the average of the total monthly `sales`:

[source,js]
--------------------------------------------------
POST /_search
{
  "size": 0,
  "aggs": {
    "sales_per_month": {
      "date_histogram": {
        "field": "date",
        "interval": "month"
      },
      "aggs": {
        "sales": {
          "sum": {
            "field": "price"
          }
        }
      }
    },
    "avg_monthly_sales": {
      "avg_bucket": {
        "buckets_path": "sales_per_month>sales" <1>
      }
    }
  }
}

--------------------------------------------------
// CONSOLE
// TEST[setup:sales]
<1> `buckets_path` instructs this avg_bucket aggregation that we want the (mean) average value of the `sales` aggregation in the
`sales_per_month` date histogram.

And the following may be the response:

[source,js]
--------------------------------------------------
{
   "took": 11,
   "timed_out": false,
   "_shards": ...,
   "hits": ...,
   "aggregations": {
      "sales_per_month": {
         "buckets": [
            {
               "key_as_string": "2015/01/01 00:00:00",
               "key": 1420070400000,
               "doc_count": 3,
               "sales": {
                  "value": 550.0
               }
            },
            {
               "key_as_string": "2015/02/01 00:00:00",
               "key": 1422748800000,
               "doc_count": 2,
               "sales": {
                  "value": 60.0
               }
            },
            {
               "key_as_string": "2015/03/01 00:00:00",
               "key": 1425168000000,
               "doc_count": 2,
               "sales": {
                  "value": 375.0
               }
            }
         ]
      },
      "avg_monthly_sales": {
          "value": 328.33333333333333
      }
   }
}
--------------------------------------------------
// TESTRESPONSE[s/"took": 11/"took": $body.took/]
// TESTRESPONSE[s/"_shards": \.\.\./"_shards": $body._shards/]
// TESTRESPONSE[s/"hits": \.\.\./"hits": $body.hits/]
