Chart.js/src/scales/scale.logarithmic.js

"use strict";

module.exports = function(Chart) {

	var helpers = Chart.helpers;

	var defaultConfig = {
		position: "left",

		// label settings
		ticks: {
			callback: function(value, index, arr) {
				var remain = value / (Math.pow(10, Math.floor(Chart.helpers.log10(value))));

				if (remain === 1 || remain === 2 || remain === 5 || index === 0 || index === arr.length - 1) {
					return value.toExponential();
				} else {
					return '';
				}
			}
		}
	};

	var LogarithmicScale = Chart.Scale.extend({
		determineDataLimits: function() {
			// Calculate Range
			this.min = null;
			this.max = null;

			if (this.options.stacked) {
				var valuesPerType = {};

				helpers.each(this.chart.data.datasets, function(dataset, datasetIndex) {
					var meta = this.chart.getDatasetMeta(datasetIndex);
					if (this.chart.isDatasetVisible(datasetIndex) && (this.isHorizontal() ? meta.xAxisID === this.id : meta.yAxisID === this.id)) {
						if (valuesPerType[meta.type] === undefined) {
							valuesPerType[meta.type] = [];
						}

						helpers.each(dataset.data, function(rawValue, index) {
							var values = valuesPerType[meta.type];
							var value = +this.getRightValue(rawValue);
							if (isNaN(value)) {
								return;
							}

							values[index] = values[index] || 0;

							if (this.options.relativePoints) {
								values[index] = 100;
							} else {
								// Don't need to split positive and negative since the log scale can't handle a 0 crossing
								values[index] += value;
							}
						}, this);
					}
				}, this);

				helpers.each(valuesPerType, function(valuesForType) {
					var minVal = helpers.min(valuesForType);
					var maxVal = helpers.max(valuesForType);
					this.min = this.min === null ? minVal : Math.min(this.min, minVal);
					this.max = this.max === null ? maxVal : Math.max(this.max, maxVal);
				}, this);

			} else {
				helpers.each(this.chart.data.datasets, function(dataset, datasetIndex) {
					var meta = this.chart.getDatasetMeta(datasetIndex);
					if (this.chart.isDatasetVisible(dataset, datasetIndex) && (this.isHorizontal() ? meta.xAxisID === this.id : meta.yAxisID === this.id)) {
						helpers.each(dataset.data, function(rawValue, index) {
							var value = +this.getRightValue(rawValue);
							if (isNaN(value)) {
								return;
							}

							if (this.min === null) {
								this.min = value;
							} else if (value < this.min) {
								this.min = value;
							}

							if (this.max === null) {
								this.max = value;
							} else if (value > this.max) {
								this.max = value;
							}
						}, this);
					}
				}, this);
			}

			this.min = this.options.ticks.min !== undefined ? this.options.ticks.min : this.min;
			this.max = this.options.ticks.max !== undefined ? this.options.ticks.max : this.max;

			if (this.min === this.max) {
				if (this.min !== 0 && this.min !== null) {
					this.min = Math.pow(10, Math.floor(helpers.log10(this.min)) - 1);
					this.max = Math.pow(10, Math.floor(helpers.log10(this.max)) + 1);
				} else {
					this.min = 1;
					this.max = 10;
				}
			}
		},
		buildTicks: function() {
			// Reset the ticks array. Later on, we will draw a grid line at these positions
			// The array simply contains the numerical value of the spots where ticks will be
			this.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 50
			// We also limit the maximum number of ticks to 11 which gives a nice 10 squares on
			// the graph

			var tickVal = this.options.ticks.min !== undefined ? this.options.ticks.min : Math.pow(10, Math.floor(helpers.log10(this.min)));

			while (tickVal < this.max) {
				this.ticks.push(tickVal);

				var exp = Math.floor(helpers.log10(tickVal));
				var significand = Math.floor(tickVal / Math.pow(10, exp)) + 1;

				if (significand === 10) {
					significand = 1;
					++exp;
				}

				tickVal = significand * Math.pow(10, exp);
			}

			var lastTick = this.options.ticks.max !== undefined ? this.options.ticks.max : tickVal;
			this.ticks.push(lastTick);

			if (this.options.position === "left" || this.options.position === "right") {
				// We are in a vertical orientation. The top value is the highest. So reverse the array
				this.ticks.reverse();
			}

			// At this point, we need to update our max and min given the tick values since we have expanded the
			// range of the scale
			this.max = helpers.max(this.ticks);
			this.min = helpers.min(this.ticks);

			if (this.options.ticks.reverse) {
				this.ticks.reverse();

				this.start = this.max;
				this.end = this.min;
			} else {
				this.start = this.min;
				this.end = this.max;
			}
		},
		convertTicksToLabels: function() {
			this.tickValues = this.ticks.slice();

			Chart.Scale.prototype.convertTicksToLabels.call(this);
		},
		// Get the correct tooltip label
		getLabelForIndex: function(index, datasetIndex) {
			return +this.getRightValue(this.chart.data.datasets[datasetIndex].data[index]);
		},
		getPixelForTick: function(index, includeOffset) {
			return this.getPixelForValue(this.tickValues[index], null, null, includeOffset);
		},
		getPixelForValue: function(value, index, datasetIndex, includeOffset) {
			var pixel;

			var newVal = +this.getRightValue(value);
			var range = helpers.log10(this.end) - helpers.log10(this.start);

			if (this.isHorizontal()) {

				if (newVal === 0) {
					pixel = this.left + this.paddingLeft;
				} else {
					var innerWidth = this.width - (this.paddingLeft + this.paddingRight);
					pixel = this.left + (innerWidth / range * (helpers.log10(newVal) - helpers.log10(this.start)));
					pixel += this.paddingLeft;
				}
			} else {
				// Bottom - top since pixels increase downard on a screen
				if (newVal === 0) {
					pixel = this.top + this.paddingTop;
				} else {
					var innerHeight = this.height - (this.paddingTop + this.paddingBottom);
					pixel = (this.bottom - this.paddingBottom) - (innerHeight / range * (helpers.log10(newVal) - helpers.log10(this.start)));
				}
			}

			return pixel;
		}

	});
	Chart.scaleService.registerScaleType("logarithmic", LogarithmicScale, defaultConfig);

};