d3article1.3

data.forEach(d => {
  d.date = new Date(d.date);
  d.percent = +d.percent;
});

x.domain(d3.extent(data, d => d.date));
y.domain([0, d3.max(data, d => d.percent)]);
colorScale.domain(d3.map(data, d => d.regionId).keys());