The radio facet type generates a single-select list of choices.
|Data Source||Where the values live (taxonomy, custom field, post attribute)|
|Parent Term||If Data Source is a hierarchical taxonomy and you want to display only child terms, enter the parent term’s ID.|
|Sort by||Sort facet choices by Facet Count, Display Value, Raw Value, or Term Order|
|Show ghosts||Ghosts are facet choices that, if clicked, would return zero results|
|Preserve ghost order||Should ghosts be kept in the same order (mixed with valid choices)?|
|Count||The number of options to display|
What are ghosts?
Ghosts are facet choices that do appear in the unfiltered results — but disappear after being filtered out. If a facet choice has no associated content, then it will never appear.