Is it possible to create a SelectionID using the Matrix data mapping?
The tutorial covers Categories (https://github.com/Microsoft/PowerBI-visuals/blob/master/Visual/Selection.md#managing-selection-selectionmanager) and the following post suggests that it's not available for Table (http://community.powerbi.com/t5/Developer/SelectionId-for-table/m-p/76506/highlight/true#M2632).