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.
An avg_bucket aggregation looks like this in isolation:
{
    "avg_bucket": {
        "buckets_path": "the_sum"
    }
}Table 7. avg_bucket Parameters
| Parameter Name | Description | Required | Default Value | 
|---|---|---|---|
| 
 | The path to the buckets we wish to find the average for (see  | Required | |
| 
 | The policy to apply when gaps are found in the data (see Dealing with gaps in the data for more details) | Optional | 
 | 
| 
 | format to apply to the output value of this aggregation | Optional | 
 | 
The following snippet calculates the average of the total monthly sales:
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"  }
    }
  }
}
      }
    }
  }
}| 
 | 
And the following may be the response:
{
   "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
      }
   }
}