Elasticsearch 5.x or above provided a special module called aggs-matrix-stats that automatically computes advanced statistics on several fields.
Executing a matrix stats aggregation
Getting ready
You need an up and running Elasticsearch installation, as we described in the Downloading and installing Elasticsearch recipe in Chapter 1, Getting Started.
To execute these commands, any HTTP client can be used, such as Curl (https://curl.haxx.se/), Postman (https://www.getpostman.com/), or similar. Using the Kibana Console is recommended, as it provides code completion and better character escaping for Elasticsearch.
To correctly execute the following commands, you will need an index populated with the ch07...
