importing legend library because d3 does not have this funciton

this library is used to create natural breaks

this line is to format object that converts any number in terms of how it is written into the format you would like to display.

put the name of the color scheme or the number of classes. Name of color scheme will give the number of colors in the list -> the number of classes is the number of colors

this is creating the color scheme. this is a list of colors, lists are in square brackets.

how close the map will be to the sides of the notebook

adjust width height and margin depending on your data (shape of shapefile)

I think this is the best projection for Chicago: d3.geoAlbers() · Source [d3-geo], because it is good for the whole US and Chicago, is just a zoomed-in view of the whole US. I think

this line of code recreates the polygons. takes the input polygons from WGS84 and turns them into the projection you use in the previous line of code. I'm going to use Albers