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log.js
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log.js
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import {ticks} from "d3-array";
import {format, formatSpecifier} from "d3-format";
import nice from "./nice.js";
import {copy, transformer} from "./continuous.js";
import {initRange} from "./init.js";
function transformLog(x) {
return Math.log(x);
}
function transformExp(x) {
return Math.exp(x);
}
function transformLogn(x) {
return -Math.log(-x);
}
function transformExpn(x) {
return -Math.exp(-x);
}
function pow10(x) {
return isFinite(x) ? +("1e" + x) : x < 0 ? 0 : x;
}
function powp(base) {
return base === 10 ? pow10
: base === Math.E ? Math.exp
: x => Math.pow(base, x);
}
function logp(base) {
return base === Math.E ? Math.log
: base === 10 && Math.log10
|| base === 2 && Math.log2
|| (base = Math.log(base), x => Math.log(x) / base);
}
function reflect(f) {
return (x, k) => -f(-x, k);
}
export function loggish(transform) {
const scale = transform(transformLog, transformExp);
const domain = scale.domain;
let base = 10;
let logs;
let pows;
function rescale() {
logs = logp(base), pows = powp(base);
if (domain()[0] < 0) {
logs = reflect(logs), pows = reflect(pows);
transform(transformLogn, transformExpn);
} else {
transform(transformLog, transformExp);
}
return scale;
}
scale.base = function(_) {
return arguments.length ? (base = +_, rescale()) : base;
};
scale.domain = function(_) {
return arguments.length ? (domain(_), rescale()) : domain();
};
scale.ticks = count => {
const d = domain();
let u = d[0];
let v = d[d.length - 1];
const r = v < u;
if (r) ([u, v] = [v, u]);
let i = logs(u);
let j = logs(v);
let k;
let t;
const n = count == null ? 10 : +count;
let z = [];
if (!(base % 1) && j - i < n) {
i = Math.floor(i), j = Math.ceil(j);
if (u > 0) for (; i <= j; ++i) {
for (k = 1; k < base; ++k) {
t = i < 0 ? k / pows(-i) : k * pows(i);
if (t < u) continue;
if (t > v) break;
z.push(t);
}
} else for (; i <= j; ++i) {
for (k = base - 1; k >= 1; --k) {
t = i > 0 ? k / pows(-i) : k * pows(i);
if (t < u) continue;
if (t > v) break;
z.push(t);
}
}
if (z.length * 2 < n) z = ticks(u, v, n);
} else {
z = ticks(i, j, Math.min(j - i, n)).map(pows);
}
return r ? z.reverse() : z;
};
scale.tickFormat = (count, specifier) => {
if (count == null) count = 10;
if (specifier == null) specifier = base === 10 ? "s" : ",";
if (typeof specifier !== "function") {
if (!(base % 1) && (specifier = formatSpecifier(specifier)).precision == null) specifier.trim = true;
specifier = format(specifier);
}
if (count === Infinity) return specifier;
const k = Math.max(1, base * count / scale.ticks().length); // TODO fast estimate?
return d => {
let i = d / pows(Math.round(logs(d)));
if (i * base < base - 0.5) i *= base;
return i <= k ? specifier(d) : "";
};
};
scale.nice = () => {
return domain(nice(domain(), {
floor: x => pows(Math.floor(logs(x))),
ceil: x => pows(Math.ceil(logs(x)))
}));
};
return scale;
}
export default function log() {
const scale = loggish(transformer()).domain([1, 10]);
scale.copy = () => copy(scale, log()).base(scale.base());
initRange.apply(scale, arguments);
return scale;
}