Figure 3.
Temporal variations in the normalised frequency of tweets belonging to Theme 1 (Topics 1 and 2), Theme 2 (Topics 3 and 4), and Theme 3 (Topics 5 and 6).
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.