src/scales/scale.linearbase.js
import {isNullOrUndef} from '../helpers/helpers.core.js';
import {almostEquals, almostWhole, niceNum, _decimalPlaces, _setMinAndMaxByKey, sign, toRadians} from '../helpers/helpers.math.js';
import Scale from '../core/core.scale.js';
import {formatNumber} from '../helpers/helpers.intl.js';
/**
* Generate a set of linear ticks for an axis
* 1. If generationOptions.min, generationOptions.max, and generationOptions.step are defined:
* if (max - min) / step is an integer, ticks are generated as [min, min + step, ..., max]
* Note that the generationOptions.maxCount setting is respected in this scenario
*
* 2. If generationOptions.min, generationOptions.max, and generationOptions.count is defined
* spacing = (max - min) / count
* Ticks are generated as [min, min + spacing, ..., max]
*
* 3. If generationOptions.count is defined
* spacing = (niceMax - niceMin) / count
*
* 4. Compute optimal spacing of ticks using niceNum algorithm
*
* @param generationOptions the options used to generate the ticks
* @param dataRange the range of the data
* @returns {object[]} array of tick objects
*/
function generateTicks(generationOptions, dataRange) {
const ticks = [];
// To get a "nice" value for the tick spacing, we will use the appropriately named
// "nice number" algorithm. See https://stackoverflow.com/questions/8506881/nice-label-algorithm-for-charts-with-minimum-ticks
// for details.
const MIN_SPACING = 1e-14;
const {bounds, step, min, max, precision, count, maxTicks, maxDigits, includeBounds} = generationOptions;
const unit = step || 1;
const maxSpaces = maxTicks - 1;
const {min: rmin, max: rmax} = dataRange;
const minDefined = !isNullOrUndef(min);
const maxDefined = !isNullOrUndef(max);
const countDefined = !isNullOrUndef(count);
const minSpacing = (rmax - rmin) / (maxDigits + 1);
let spacing = niceNum((rmax - rmin) / maxSpaces / unit) * unit;
let factor, niceMin, niceMax, numSpaces;
// Beyond MIN_SPACING floating point numbers being to lose precision
// such that we can't do the math necessary to generate ticks
if (spacing < MIN_SPACING && !minDefined && !maxDefined) {
return [{value: rmin}, {value: rmax}];
}
numSpaces = Math.ceil(rmax / spacing) - Math.floor(rmin / spacing);
if (numSpaces > maxSpaces) {
// If the calculated num of spaces exceeds maxNumSpaces, recalculate it
spacing = niceNum(numSpaces * spacing / maxSpaces / unit) * unit;
}
if (!isNullOrUndef(precision)) {
// If the user specified a precision, round to that number of decimal places
factor = Math.pow(10, precision);
spacing = Math.ceil(spacing * factor) / factor;
}
if (bounds === 'ticks') {
niceMin = Math.floor(rmin / spacing) * spacing;
niceMax = Math.ceil(rmax / spacing) * spacing;
} else {
niceMin = rmin;
niceMax = rmax;
}
if (minDefined && maxDefined && step && almostWhole((max - min) / step, spacing / 1000)) {
// Case 1: If min, max and stepSize are set and they make an evenly spaced scale use it.
// spacing = step;
// numSpaces = (max - min) / spacing;
// Note that we round here to handle the case where almostWhole translated an FP error
numSpaces = Math.round(Math.min((max - min) / spacing, maxTicks));
spacing = (max - min) / numSpaces;
niceMin = min;
niceMax = max;
} else if (countDefined) {
// Cases 2 & 3, we have a count specified. Handle optional user defined edges to the range.
// Sometimes these are no-ops, but it makes the code a lot clearer
// and when a user defined range is specified, we want the correct ticks
niceMin = minDefined ? min : niceMin;
niceMax = maxDefined ? max : niceMax;
numSpaces = count - 1;
spacing = (niceMax - niceMin) / numSpaces;
} else {
// Case 4
numSpaces = (niceMax - niceMin) / spacing;
// If very close to our rounded value, use it.
if (almostEquals(numSpaces, Math.round(numSpaces), spacing / 1000)) {
numSpaces = Math.round(numSpaces);
} else {
numSpaces = Math.ceil(numSpaces);
}
}
// The spacing will have changed in cases 1, 2, and 3 so the factor cannot be computed
// until this point
const decimalPlaces = Math.max(
_decimalPlaces(spacing),
_decimalPlaces(niceMin)
);
factor = Math.pow(10, isNullOrUndef(precision) ? decimalPlaces : precision);
niceMin = Math.round(niceMin * factor) / factor;
niceMax = Math.round(niceMax * factor) / factor;
let j = 0;
if (minDefined) {
if (includeBounds && niceMin !== min) {
ticks.push({value: min});
if (niceMin < min) {
j++; // Skip niceMin
}
// If the next nice tick is close to min, skip it
if (almostEquals(Math.round((niceMin + j * spacing) * factor) / factor, min, relativeLabelSize(min, minSpacing, generationOptions))) {
j++;
}
} else if (niceMin < min) {
j++;
}
}
for (; j < numSpaces; ++j) {
const tickValue = Math.round((niceMin + j * spacing) * factor) / factor;
if (maxDefined && tickValue > max) {
break;
}
ticks.push({value: tickValue});
}
if (maxDefined && includeBounds && niceMax !== max) {
// If the previous tick is too close to max, replace it with max, else add max
if (ticks.length && almostEquals(ticks[ticks.length - 1].value, max, relativeLabelSize(max, minSpacing, generationOptions))) {
ticks[ticks.length - 1].value = max;
} else {
ticks.push({value: max});
}
} else if (!maxDefined || niceMax === max) {
ticks.push({value: niceMax});
}
return ticks;
}
function relativeLabelSize(value, minSpacing, {horizontal, minRotation}) {
const rad = toRadians(minRotation);
const ratio = (horizontal ? Math.sin(rad) : Math.cos(rad)) || 0.001;
const length = 0.75 * minSpacing * ('' + value).length;
return Math.min(minSpacing / ratio, length);
}
export default class LinearScaleBase extends Scale {
constructor(cfg) {
super(cfg);
/** @type {number} */
this.start = undefined;
/** @type {number} */
this.end = undefined;
/** @type {number} */
this._startValue = undefined;
/** @type {number} */
this._endValue = undefined;
this._valueRange = 0;
}
parse(raw, index) { // eslint-disable-line no-unused-vars
if (isNullOrUndef(raw)) {
return null;
}
if ((typeof raw === 'number' || raw instanceof Number) && !isFinite(+raw)) {
return null;
}
return +raw;
}
handleTickRangeOptions() {
const {beginAtZero} = this.options;
const {minDefined, maxDefined} = this.getUserBounds();
let {min, max} = this;
const setMin = v => (min = minDefined ? min : v);
const setMax = v => (max = maxDefined ? max : v);
if (beginAtZero) {
const minSign = sign(min);
const maxSign = sign(max);
if (minSign < 0 && maxSign < 0) {
setMax(0);
} else if (minSign > 0 && maxSign > 0) {
setMin(0);
}
}
if (min === max) {
let offset = max === 0 ? 1 : Math.abs(max * 0.05);
setMax(max + offset);
if (!beginAtZero) {
setMin(min - offset);
}
}
this.min = min;
this.max = max;
}
getTickLimit() {
const tickOpts = this.options.ticks;
// eslint-disable-next-line prefer-const
let {maxTicksLimit, stepSize} = tickOpts;
let maxTicks;
if (stepSize) {
maxTicks = Math.ceil(this.max / stepSize) - Math.floor(this.min / stepSize) + 1;
if (maxTicks > 1000) {
console.warn(`scales.${this.id}.ticks.stepSize: ${stepSize} would result generating up to ${maxTicks} ticks. Limiting to 1000.`);
maxTicks = 1000;
}
} else {
maxTicks = this.computeTickLimit();
maxTicksLimit = maxTicksLimit || 11;
}
if (maxTicksLimit) {
maxTicks = Math.min(maxTicksLimit, maxTicks);
}
return maxTicks;
}
/**
* @protected
*/
computeTickLimit() {
return Number.POSITIVE_INFINITY;
}
buildTicks() {
const opts = this.options;
const tickOpts = opts.ticks;
// Figure out what the max number of ticks we can support it is based on the size of
// the axis area. For now, we say that the minimum tick spacing in pixels must be 40
// We also limit the maximum number of ticks to 11 which gives a nice 10 squares on
// the graph. Make sure we always have at least 2 ticks
let maxTicks = this.getTickLimit();
maxTicks = Math.max(2, maxTicks);
const numericGeneratorOptions = {
maxTicks,
bounds: opts.bounds,
min: opts.min,
max: opts.max,
precision: tickOpts.precision,
step: tickOpts.stepSize,
count: tickOpts.count,
maxDigits: this._maxDigits(),
horizontal: this.isHorizontal(),
minRotation: tickOpts.minRotation || 0,
includeBounds: tickOpts.includeBounds !== false
};
const dataRange = this._range || this;
const ticks = generateTicks(numericGeneratorOptions, dataRange);
// At this point, we need to update our max and min given the tick values,
// since we probably have expanded the range of the scale
if (opts.bounds === 'ticks') {
_setMinAndMaxByKey(ticks, this, 'value');
}
if (opts.reverse) {
ticks.reverse();
this.start = this.max;
this.end = this.min;
} else {
this.start = this.min;
this.end = this.max;
}
return ticks;
}
/**
* @protected
*/
configure() {
const ticks = this.ticks;
let start = this.min;
let end = this.max;
super.configure();
if (this.options.offset && ticks.length) {
const offset = (end - start) / Math.max(ticks.length - 1, 1) / 2;
start -= offset;
end += offset;
}
this._startValue = start;
this._endValue = end;
this._valueRange = end - start;
}
getLabelForValue(value) {
return formatNumber(value, this.chart.options.locale, this.options.ticks.format);
}
}