color4 = {
const values = [...deaths.values()];
const max = Math.max(d3.max(values, ([a, b]) => a / b), d3.max(values, ([a, b]) => b / a));
return d3.scaleLog()
.domain([1 / max, 1, max])
.range([-1, 0, 1])
.interpolate((a, b) => a < 0
? t => d3.interpolateBlues(1 - t)
: t => d3.interpolateReds(t));
}