We love a good infographic. We loved the Twitter World Cup one and we love this "Pulse of the Nation" one just as much.

Clever bods from Northeastern University and Harvard University have analysed tweets from September 2006 to August 2009 - over 300 million in total - to create these incredible density-preserving cartograms.

These cartograms are maps that use tweet volumes to demonstrate land area, providing hot spots where more tweeting is being done and making areas appear larger than they actually are.

Along with data mashed in from the Census Bureau and Google Maps, the words used within the tweets are deciphered against a word list to associate moods to the display.

The result is this brilliant time-lapse video which shows how the moods of tweeters in the US changes over the course of a day and week.

The results show that there is a mid-week slump - Thursday afternoons are a low point - and, not surprisingly, people are happiest on Saturday evenings. Day-wise, people are most happy during early mornings (?!?) as well as in the evenings.

For a full breakdown look at the awesome poster that has been created to compliment the video.