Each chart shows taxi data aggregated by day of the week and hour of the day for a given month. For example, on Thursdays in January at 8pm there were 163,297 total rides. During 2013, there were 171,976,998 total rides. I used Apache Spark running on a 14 node cluster to run aggregations across the data set. The data is available via Chris Wong here. I leveraged Peter Cook's circular heat chart library for the visualization. You can find my code on my github.