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124 lines
3.9 KiB
JavaScript
124 lines
3.9 KiB
JavaScript
/*!
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* chartjs-plugin-trendline.js
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* Version: 0.1.3
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*
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* Copyright 2017 Marcus Alsterfjord
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* Released under the MIT license
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* https://github.com/Makanz/chartjs-plugin-trendline/blob/master/README.md
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*
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* Mod by: vesal: accept also xy-data so works with scatter
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*/
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var pluginTrendlineLinear = {
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beforeDraw: function(chartInstance) {
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var yScale;
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var xScale;
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for (var axis in chartInstance.scales) {
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if ( axis[0] == 'x')
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xScale = chartInstance.scales[axis];
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else
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yScale = chartInstance.scales[axis];
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if ( xScale && yScale ) break;
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}
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var ctx = chartInstance.chart.ctx;
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chartInstance.data.datasets.forEach(function(dataset, index) {
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if (dataset.trendlineLinear && chartInstance.isDatasetVisible(index)) {
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var datasetMeta = chartInstance.getDatasetMeta(index);
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addFitter(datasetMeta, ctx, dataset, xScale, yScale);
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}
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});
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ctx.setLineDash([]);
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}
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};
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function addFitter(datasetMeta, ctx, dataset, xScale, yScale) {
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if(datasetMeta.data == [] || datasetMeta.data == null || datasetMeta.data.length == 0) return;
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var style = dataset.trendlineLinear.style || dataset.borderColor;
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var lineWidth = dataset.trendlineLinear.width || dataset.borderWidth;
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var lineStyle = dataset.trendlineLinear.lineStyle || "solid";
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style = (style !== undefined) ? style : "rgba(169,169,169, .6)";
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lineWidth = (lineWidth !== undefined) ? lineWidth : 3;
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var fitter = new LineFitter();
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var lastIndex = dataset.data.length - 1;
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var startPos = datasetMeta.data[0]._model.x;
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var endPos = datasetMeta.data[lastIndex]._model.x;
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var xy = false;
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if ( dataset.data && typeof dataset.data[0] === 'object') xy = true;
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dataset.data.forEach(function(data, index) {
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if(data == null)
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return;
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if ( xy ) fitter.add(data.x, data.y);
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else fitter.add(index, data);
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});
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var x1 = xScale.getPixelForValue(fitter.minx);
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var x2 = xScale.getPixelForValue(fitter.maxx);
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var y1 = yScale.getPixelForValue(fitter.f(fitter.minx));
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var y2 = yScale.getPixelForValue(fitter.f(fitter.maxx));
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if ( !xy ) { x1 = startPos; x2 = endPos; }
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var drawBottom = datasetMeta.controller.chart.chartArea.bottom;
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var chartWidth = datasetMeta.controller.chart.width;
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if(y1 > drawBottom) { // Left side is below zero
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var diff = y1 - drawBottom;
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var lineHeight = y1 - y2;
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var overlapPercentage = diff / lineHeight;
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var addition = chartWidth * overlapPercentage;
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y1 = drawBottom;
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x1 = (x1 + addition);
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} else if(y2 > drawBottom) { // right side is below zero
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var diff = y2 - drawBottom;
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var lineHeight = y2 - y1;
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var overlapPercentage = diff / lineHeight;
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var subtraction = chartWidth - (chartWidth * overlapPercentage);
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y2 = drawBottom;
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x2 = chartWidth - (x2 - subtraction);
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}
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ctx.lineWidth = lineWidth;
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if (lineStyle === "dotted") { ctx.setLineDash([2, 3]); }
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ctx.beginPath();
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ctx.moveTo(x1, y1);
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ctx.lineTo(x2, y2);
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ctx.strokeStyle = style;
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ctx.stroke();
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}
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Chart.plugins.register(pluginTrendlineLinear);
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function LineFitter() {
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this.count = 0;
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this.sumX = 0;
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this.sumX2 = 0;
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this.sumXY = 0;
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this.sumY = 0;
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this.minx = 1e100;
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this.maxx = -1e100;
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}
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LineFitter.prototype = {
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'add': function (x, y) {
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this.count++;
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this.sumX += x;
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this.sumX2 += x * x;
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this.sumXY += x * y;
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this.sumY += y;
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if ( x < this.minx ) this.minx = x;
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if ( x > this.maxx ) this.maxx = x;
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},
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'f': function (x) {
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var det = this.count * this.sumX2 - this.sumX * this.sumX;
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var offset = (this.sumX2 * this.sumY - this.sumX * this.sumXY) / det;
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var scale = (this.count * this.sumXY - this.sumX * this.sumY) / det;
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return offset + x * scale;
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}
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};
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