Some modifications (adaptating it for d3 v4, adding support for legend) around the code from "A different look for the D3 radar chart".
forked from mthh's block: Radar Chart d3 v4
forked from Coola85's block: Radar Chart d3 v4
https://d3js.org/d3.v5.min.js
https://d3js.org/d3-path.v1.min.js