Data
I downloaded the Citbike ridership data from May 2016, and dropped all columns from the data except for the usertype for each ride and the date and time of the ride. There are two types of users - subscribers, who pay a monthly or yearly subscription for Citibike, and 'customers' who pay per ride or per day. I have assumed that subscribers are local New Yorkers and customers are tourists. I then filtered the data using the .groupby() function on python pandas to count the number of subscribers and tourists travelling on each day of the week (see Fig 1).