Discovering Social Events through Online Attention
Figure 2
Time evolution of the number of tweets (top), number of hashtags (middle), and Herfindahl-Hirsch Index (HHI) parameter (bottom) for the OWS dataset, on a daily time horizon.
The HHI calculates how diverse the discussion is on Twitter, by calculating how many messages are associated with a given hashtag, and ranges from a value of 0, for highly diverse discussion, to 1, when all messages are focused on only one hashtag.