  We introduce Hoop Diagrams, a new visualization technique for set data. Hoop
Diagrams are a circular visualization with hoops representing sets and sectors
representing set intersections. We present an interactive tool for drawing Hoop
Diagrams and describe a user study comparing them with Linear Diagrams. The
results show only small differences, with users answering questions more
quickly with Linear Diagrams, but answering some questions more accurately with
Hoop Diagrams. Interaction data indicates that those using set order and
intersection highlighting were more successful at answering questions, but
those who used other interactions had a slower response. The similarity in
usability suggests that the diagram type should be chosen based on the
presentation method. Linear Diagrams increase in the horizontal direction with
the number of intersections, leading to difficulties fitting on a screen. Hoop
Diagrams al-ways have a square aspect ratio.
