You can use Sankey graphs to plot two categories against each other. An example use case could be:
For my search on "smart city", I want to see which emerging technologies are connected to which companies, focusing on Technology Blogs.
Similar to network graphs, you can open Sankey graphs by clicking the "Sankey graph" icon...
...next to the tag cloud:
This screenshot is from a search on "smart city" in technology blogs.
Then, in the Sankey graph, you can select an entity class for the left and one for the right side, and then confirm ("Set left and right"):
In order to be able to scroll down, you can right-click on any entity and fix the display:
You can click on any entity to get to documents containing the entity, or on a connection between two entities to get to documents containing both connected entities.
By clicking "CSV (Excel)", you can export the Sankey chart data as a connection matrix:
In the connection matrix, the left and right entities form rows and columns, and the connection strengths are represented by cell values.