export default function(domain, count, specifier) {
var start = domain[0],
stop = domain[domain.length - 1],
step = tickStep(start, stop, count == null ? 10 : count);
if (specifier == null) {
specifier = ",." + precisionFixed(step) + "f";
} else {
switch (specifier = formatSpecifier(specifier), specifier.type) {
case "s": {
var value = Math.max(Math.abs(start), Math.abs(stop));
if (specifier.precision == null) specifier.precision = precisionPrefix(step, value);
return formatPrefix(specifier, value);
}
case "":
case "e":
case "g":
case "p":
case "r": {
if (specifier.precision == null) specifier.precision = precisionRound(step, Math.max(Math.abs(start), Math.abs(stop))) - (specifier.type === "e");
break;
}
case "f":
case "%": {
if (specifier.precision == null) specifier.precision = precisionFixed(step) - (specifier.type === "%") * 2;
break;
}
}
}
return format(specifier);
};
scale.nice = function(count) {
var d = domain(),
i = d.length - 1,
n = count == null ? 10 : count,
start = d[0],
stop = d[i],
step = tickStep(start, stop, n);
if (step) {
step = tickStep(Math.floor(start / step) * step, Math.ceil(stop / step) * step, n);
d[0] = Math.floor(start / step) * step;
d[i] = Math.ceil(stop / step) * step;
domain(d);
}
return scale;
};
function tickInterval(interval, start, stop, step) {
if (interval == null) interval = 10;
// If a desired tick count is specified, pick a reasonable tick interval
// based on the extent of the domain and a rough estimate of tick size.
// Otherwise, assume interval is already a time interval and use it.
if (typeof interval === "number") {
var target = Math.abs(stop - start) / interval,
i = bisector(function(i) { return i[2]; }).right(tickIntervals, target);
if (i === tickIntervals.length) {
step = tickStep(start / durationYear, stop / durationYear, interval);
interval = year;
} else if (i) {
i = tickIntervals[target / tickIntervals[i - 1][2] < tickIntervals[i][2] / target ? i - 1 : i];
step = i[1];
interval = i[0];
} else {
step = Math.max(tickStep(start, stop, interval), 1);
interval = millisecond;
}
}
return step == null ? interval : interval.every(step);
}