curves = d3
.cross(range(3, 5, .1), range(.1, .5, .05).reverse())
.map(([l, k]) => {
const L = 5 * 10 ** l;
const x0 = dLogisticFindX0(L, k, 0, threshold);
const fn = dLogistic(x0, L, k);
const peak = [x0, fn(x0)];
const data = range(0, domain.length, .5).map(d => [d, fn(d)]);
return { L, k, x0, peak, data };
})