support adjacency matrix aggregation in Kibana

[AlonaNadler]

Today the user can use filters aggregation to slice the data in a custom way that provides non mutually exclusive buckets. But if the user needs a combination of filters to know how many documents fall within any combination of filters, it is supported by Elasticsearch (https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-bucket-adjacency-matrix-aggregation.html) but not in Kibana

This kind of matrix can be very useful in pie charts, bar charts and area charts as well as tables.
Example when analyzing usage (Venn or Funnel visualization) users might want to know who uses A, B or C but also the combination A&B B&C and A&C

In addition, this capability might come in handy with Graph to visualize relationships

[elasticmachine]

Pinging @elastic/kibana-app

[wylieconlon]

Supporting this aggregation might mean one of two things:

1. Add adjacency matrix to all charts that support the filters aggregation today, such as bar charts. These can support the flattened version of the adjacency matrix. We would need to rename the response, for example Custom Label 1 & Custom Label 2
2. Add a correlation matrix chart type, described in detail here Annotated Heatmap of a Correlation Matrix elastic-charts#263

[ghudgins]

could be interesting to consider this as 1) a part of filters 2) its own quick function so it could be a part of heatmap visualization....

[timductive]

Closing this because it's not planned to be resolved in the foreseeable future. It will be tracked in our Icebox and will be re-opened if our priorities change. Feel free to re-open if you think it should be melted sooner.