scale.logarithmic.js

'use strict';

var defaults = require('../core/core.defaults');
var helpers = require('../helpers/index');
var Scale = require('../core/core.scale');
var Ticks = require('../core/core.ticks');

var valueOrDefault = helpers.valueOrDefault;

/**
 * Generate a set of logarithmic ticks
 * @param generationOptions the options used to generate the ticks
 * @param dataRange the range of the data
 * @returns {number[]} array of tick values
 */
function generateTicks(generationOptions, dataRange) {
	var ticks = [];

	var tickVal = valueOrDefault(generationOptions.min, Math.pow(10, Math.floor(helpers.log10(dataRange.min))));

	var endExp = Math.floor(helpers.log10(dataRange.max));
	var endSignificand = Math.ceil(dataRange.max / Math.pow(10, endExp));
	var exp, significand;

	if (tickVal === 0) {
		exp = Math.floor(helpers.log10(dataRange.minNotZero));
		significand = Math.floor(dataRange.minNotZero / Math.pow(10, exp));

		ticks.push(tickVal);
		tickVal = significand * Math.pow(10, exp);
	} else {
		exp = Math.floor(helpers.log10(tickVal));
		significand = Math.floor(tickVal / Math.pow(10, exp));
	}
	var precision = exp < 0 ? Math.pow(10, Math.abs(exp)) : 1;

	do {
		ticks.push(tickVal);

		++significand;
		if (significand === 10) {
			significand = 1;
			++exp;
			precision = exp >= 0 ? 1 : precision;
		}

		tickVal = Math.round(significand * Math.pow(10, exp) * precision) / precision;
	} while (exp < endExp || (exp === endExp && significand < endSignificand));

	var lastTick = valueOrDefault(generationOptions.max, tickVal);
	ticks.push(lastTick);

	return ticks;
}

var defaultConfig = {
	position: 'left',

	// label settings
	ticks: {
		callback: Ticks.formatters.logarithmic
	}
};

// TODO(v3): change this to positiveOrDefault
function nonNegativeOrDefault(value, defaultValue) {
	return helpers.isFinite(value) && value >= 0 ? value : defaultValue;
}

module.exports = Scale.extend({
	determineDataLimits: function() {
		var me = this;
		var opts = me.options;
		var chart = me.chart;
		var datasets = chart.data.datasets;
		var isHorizontal = me.isHorizontal();
		function IDMatches(meta) {
			return isHorizontal ? meta.xAxisID === me.id : meta.yAxisID === me.id;
		}
		var datasetIndex, meta, value, data, i, ilen;

		// Calculate Range
		me.min = Number.POSITIVE_INFINITY;
		me.max = Number.NEGATIVE_INFINITY;
		me.minNotZero = Number.POSITIVE_INFINITY;

		var hasStacks = opts.stacked;
		if (hasStacks === undefined) {
			for (datasetIndex = 0; datasetIndex < datasets.length; datasetIndex++) {
				meta = chart.getDatasetMeta(datasetIndex);
				if (chart.isDatasetVisible(datasetIndex) && IDMatches(meta) &&
					meta.stack !== undefined) {
					hasStacks = true;
					break;
				}
			}
		}

		if (opts.stacked || hasStacks) {
			var valuesPerStack = {};

			for (datasetIndex = 0; datasetIndex < datasets.length; datasetIndex++) {
				meta = chart.getDatasetMeta(datasetIndex);
				var key = [
					meta.type,
					// we have a separate stack for stack=undefined datasets when the opts.stacked is undefined
					((opts.stacked === undefined && meta.stack === undefined) ? datasetIndex : ''),
					meta.stack
				].join('.');

				if (chart.isDatasetVisible(datasetIndex) && IDMatches(meta)) {
					if (valuesPerStack[key] === undefined) {
						valuesPerStack[key] = [];
					}

					data = datasets[datasetIndex].data;
					for (i = 0, ilen = data.length; i < ilen; i++) {
						var values = valuesPerStack[key];
						value = me._parseValue(data[i]);
						// invalid, hidden and negative values are ignored
						if (isNaN(value.min) || isNaN(value.max) || meta.data[i].hidden || value.min < 0 || value.max < 0) {
							continue;
						}
						values[i] = values[i] || 0;
						values[i] += value.max;
					}
				}
			}

			helpers.each(valuesPerStack, function(valuesForType) {
				if (valuesForType.length > 0) {
					var minVal = helpers.min(valuesForType);
					var maxVal = helpers.max(valuesForType);
					me.min = Math.min(me.min, minVal);
					me.max = Math.max(me.max, maxVal);
				}
			});

		} else {
			for (datasetIndex = 0; datasetIndex < datasets.length; datasetIndex++) {
				meta = chart.getDatasetMeta(datasetIndex);
				if (chart.isDatasetVisible(datasetIndex) && IDMatches(meta)) {
					data = datasets[datasetIndex].data;
					for (i = 0, ilen = data.length; i < ilen; i++) {
						value = me._parseValue(data[i]);
						// invalid, hidden and negative values are ignored
						if (isNaN(value.min) || isNaN(value.max) || meta.data[i].hidden || value.min < 0 || value.max < 0) {
							continue;
						}

						me.min = Math.min(value.min, me.min);
						me.max = Math.max(value.max, me.max);

						if (value.min !== 0) {
							me.minNotZero = Math.min(value.min, me.minNotZero);
						}
					}
				}
			}
		}

		me.min = helpers.isFinite(me.min) ? me.min : null;
		me.max = helpers.isFinite(me.max) ? me.max : null;
		me.minNotZero = helpers.isFinite(me.minNotZero) ? me.minNotZero : null;

		// Common base implementation to handle ticks.min, ticks.max
		this.handleTickRangeOptions();
	},

	handleTickRangeOptions: function() {
		var me = this;
		var tickOpts = me.options.ticks;
		var DEFAULT_MIN = 1;
		var DEFAULT_MAX = 10;

		me.min = nonNegativeOrDefault(tickOpts.min, me.min);
		me.max = nonNegativeOrDefault(tickOpts.max, me.max);

		if (me.min === me.max) {
			if (me.min !== 0 && me.min !== null) {
				me.min = Math.pow(10, Math.floor(helpers.log10(me.min)) - 1);
				me.max = Math.pow(10, Math.floor(helpers.log10(me.max)) + 1);
			} else {
				me.min = DEFAULT_MIN;
				me.max = DEFAULT_MAX;
			}
		}
		if (me.min === null) {
			me.min = Math.pow(10, Math.floor(helpers.log10(me.max)) - 1);
		}
		if (me.max === null) {
			me.max = me.min !== 0
				? Math.pow(10, Math.floor(helpers.log10(me.min)) + 1)
				: DEFAULT_MAX;
		}
		if (me.minNotZero === null) {
			if (me.min > 0) {
				me.minNotZero = me.min;
			} else if (me.max < 1) {
				me.minNotZero = Math.pow(10, Math.floor(helpers.log10(me.max)));
			} else {
				me.minNotZero = DEFAULT_MIN;
			}
		}
	},

	buildTicks: function() {
		var me = this;
		var tickOpts = me.options.ticks;
		var reverse = !me.isHorizontal();

		var generationOptions = {
			min: nonNegativeOrDefault(tickOpts.min),
			max: nonNegativeOrDefault(tickOpts.max)
		};
		var ticks = me.ticks = generateTicks(generationOptions, me);

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

		if (tickOpts.reverse) {
			reverse = !reverse;
			me.start = me.max;
			me.end = me.min;
		} else {
			me.start = me.min;
			me.end = me.max;
		}
		if (reverse) {
			ticks.reverse();
		}
	},

	convertTicksToLabels: function() {
		this.tickValues = this.ticks.slice();

		Scale.prototype.convertTicksToLabels.call(this);
	},

	// Get the correct tooltip label
	getLabelForIndex: function(index, datasetIndex) {
		return this._getScaleLabel(this.chart.data.datasets[datasetIndex].data[index]);
	},

	getPixelForTick: function(index) {
		return this.getPixelForValue(this.tickValues[index]);
	},

	/**
	 * Returns the value of the first tick.
	 * @param {number} value - The minimum not zero value.
	 * @return {number} The first tick value.
	 * @private
	 */
	_getFirstTickValue: function(value) {
		var exp = Math.floor(helpers.log10(value));
		var significand = Math.floor(value / Math.pow(10, exp));

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

	getPixelForValue: function(value) {
		var me = this;
		var tickOpts = me.options.ticks;
		var reverse = tickOpts.reverse;
		var log10 = helpers.log10;
		var firstTickValue = me._getFirstTickValue(me.minNotZero);
		var offset = 0;
		var innerDimension, pixel, start, end, sign;

		value = +me.getRightValue(value);
		if (reverse) {
			start = me.end;
			end = me.start;
			sign = -1;
		} else {
			start = me.start;
			end = me.end;
			sign = 1;
		}
		if (me.isHorizontal()) {
			innerDimension = me.width;
			pixel = reverse ? me.right : me.left;
		} else {
			innerDimension = me.height;
			sign *= -1; // invert, since the upper-left corner of the canvas is at pixel (0, 0)
			pixel = reverse ? me.top : me.bottom;
		}
		if (value !== start) {
			if (start === 0) { // include zero tick
				offset = valueOrDefault(tickOpts.fontSize, defaults.global.defaultFontSize);
				innerDimension -= offset;
				start = firstTickValue;
			}
			if (value !== 0) {
				offset += innerDimension / (log10(end) - log10(start)) * (log10(value) - log10(start));
			}
			pixel += sign * offset;
		}
		return pixel;
	},

	getValueForPixel: function(pixel) {
		var me = this;
		var tickOpts = me.options.ticks;
		var reverse = tickOpts.reverse;
		var log10 = helpers.log10;
		var firstTickValue = me._getFirstTickValue(me.minNotZero);
		var innerDimension, start, end, value;

		if (reverse) {
			start = me.end;
			end = me.start;
		} else {
			start = me.start;
			end = me.end;
		}
		if (me.isHorizontal()) {
			innerDimension = me.width;
			value = reverse ? me.right - pixel : pixel - me.left;
		} else {
			innerDimension = me.height;
			value = reverse ? pixel - me.top : me.bottom - pixel;
		}
		if (value !== start) {
			if (start === 0) { // include zero tick
				var offset = valueOrDefault(tickOpts.fontSize, defaults.global.defaultFontSize);
				value -= offset;
				innerDimension -= offset;
				start = firstTickValue;
			}
			value *= log10(end) - log10(start);
			value /= innerDimension;
			value = Math.pow(10, log10(start) + value);
		}
		return value;
	}
});

// INTERNAL: static default options, registered in src/index.js
module.exports._defaults = defaultConfig;