) (which you can do from the Twitter home page when you're logged in, or from the search page) is a great way to find out what people are talking about around the world. Often, when a topic is trending on Twitter, it means that some major bit of news is unfolding about the trending term. But news that has global appeal might not be relevant to you when viewed through a local lens. A new site called Happn.in tracks trends locally on Twitter in 52 different metro areas around the world.
Happn.in tracks local Twitter users in 52 global cities, and computes a list of the top 10 phrases used in each city every hour. The top phrases used significantly more often that hour than the last are compiled into a list of trends. As Happn.in explains, "A phrase's hotness is calculated with the ratio of the [percentage of users who used that phrase during the past hour] to the [mean percentage of users who used that phrase over the past week]. Phrases decay exponentially, and quickly drop from the list once they have stopped being used."
Or, in other words, at any given time you should be seeing a list of the top trending topics in your area over the past hour. This is important because very often things trend locally that would be important to residents of that area, but not to the rest of the world. Without a way to track those local trends, it might be difficult to find that sort of news.
For example, in the city of Montreal today news that the Canadiens hockey team has named a new head coach is one of the top trends. That's clearly very important to many residents of the hockey-crazed Canadian city, but not very trend-worthy outside of that geographic area. If you live in Montreal and had no way of tracking local trends, you might miss that news on Twitter.
Happen.in offers a special Twitter account for each of the 52 cities it currently tracks, allowing interested users to get automatic trend updates via Twitter every few hours.
Local trend data could be very valuable for research purposes - for example, being able to track how information about a specific topic spread across Twitter within certain areas or from place to place. Happn.in's Labs page offers a glimpse into that potential, letting users load up trends for any past date (back to May 12, when the site launched). Additionally, more comprehensive data sets are available to researchers on request.
In the future, Happn.in plans to extend trend tracking beyond local metro areas to other groups of users, such as people with common interests, or presumably, the people you follow. Being able to track trending topics within a specific, predefined subset of topically-linked users could be infinitely valuable in terms of exposing relevant breaking news on Twitter.
