"This graph shows how positively or negatively people felt about a river over time. When the line goes up, people expressed positive feelings about the river. If it goes down, then they expressed negative feelings. Using natural language processing on millions of tweets, we assign each tweet mentioning a river by name a sentiment score between 5 (very positive) and minus-5 (very negative). The graph displays the monthly mean score. Click and zoom to increase the temporal resolution to daily view. Double-click to return to the default view. Hint: when you tweet about a river, make sure to mention its full name. Then our algorithm is more likely to pick up your tweet."
Added language to increase usability:
"This graph shows how positively or negatively people felt about a river over time. When the line goes up, people expressed positive feelings about the river. If it goes down, then they expressed negative feelings. Using natural language processing on millions of tweets, we assign each tweet mentioning a river by name a sentiment score between 5 (very positive) and minus-5 (very negative). The graph displays the monthly mean score. Click and zoom to increase the temporal resolution to daily view. Double-click to return to the default view. Hint: when you tweet about a river, make sure to mention its full name. Then our algorithm is more likely to pick up your tweet."