a = {
let colors = ["#ffffd4", "#fe9929", "#8c2d04"];
let density_thresholds = d3.range(0, 1, .1);
let linearColorScale = d3
.scaleLinear()
.domain(d3.range(0, 1, 1 / colors.length))
.range(colors);
let quantz = d3.quantize(linearColorScale, density_thresholds.length + 1);
return {
quantz: quantz,
density_thresholds: density_thresholds,
colorScale: linearColorScale
};
}