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Variance Aggregation

A single-value metrics aggregation that computes the variance of numeric values that are extracted from the aggregated documents.

Structuring

The following snippet captures the structure of variance aggregations:

"<aggregation_name>": {
  "_variance": {
    "_field": "<field_name>"
  },
  ...
}

Field

The <field_name> in the _field parameter defines the specific field from which the numeric values in the documents are extracted and used to compute the returned variance.

Assuming the data consists of documents representing bank accounts, as shown in the sample dataset of Data Exploration section:

SEARCH /bank/
{
  "_query": "*",
  "_limit": 0,
  "_check_at_least": 1000,
  "_aggs": {
    "balance_variance": {
      "_variance": {
        "_field": "balance"
      }
    }
  }
}

The above aggregation computes the balance variance over all documents. The above will return the following:

2267334.7731415

  "aggregations": {
    "_doc_count": 1000,
    "balance_variance": {
      "_variance": 2267334.7731415
    }
  }, ...

The name of the aggregation (balance_variance above) also serves as the key by which the aggregation result can be retrieved from the returned response.

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