By Laëtitia Pfaender on 26 may 2014

For the Digital Eternity Project, we queried the Weibo API during the period of Qing Ming festival. This traditional Chinese festival (清明节 Qīngmíng Jíe in Mandarin Chinese) also known as Ancestors’ Day held on April 5 this year. We collected about 245,000 messages created between April 1 and April 9 and localized in Shanghai. These messages aim to be analyzed for their content but they also represent a convenient dataset to explore the variation of the number of messages posted along the day across the city.

Therefore, based on the creation date of these messages, we could make the bar chart of the bottom portion, showing the number of messages per hour of the day.

As the messages are also localized, we could position them on a map of Shanghai to compare the activity registered in the different areas. Thus, we re-created a tessellation made with 4 km diameter cells centered on the 85 locations used to query the Weibo API. Each message was counted in the cell whose center was the closest to its GPS location. The top portion shows the resulting map without regard to their creation time.

Then we can combine these two informations, namely location and time, to explore the variation of activity in the various areas along the day. To see the localized activity along the day, you can mouse over the bars of the bar chart and the map will update according to the hour. It would have been as easy to create an animation that would play the 24 maps but we found that it was more exploration oriented to be able to play at will the differences between successive hours.

This visualization is built on two JavaScript libraries: D3.js for the bar chart and Mapbox.js for the maps. To learn more about how all the code works, a tutorial is available on our blog.