Your job is to
1. Read in the data using D3.
2. Draw the locations as circles, and make the radius of circles proportional to the total trading amount.
3. Draw the trading as lines between the locations, and make the thickness of lines proportional to the amount.
4. Interactive tooltip:
1. When the mouse hovers on a circle, the name of the location and its total trading amount should be displayed in a tooltip.
2. When mouse hovers on a line, the two names of its linked locations and the trading amount should be displayed in a tooltip.
5. Circles should be rendered on top of lines.
Your code should be generic and work with other data files of similar format, i.e. your code should be able to load and visualise the two data files attached without any changes except the file name.
The data is available at the bottom of the page.
