ChartJS 中线段的不同颜色

Question

I have a time line chart type. I would like to define color on every step between two dots depending on dataset object values.

In my dataset data array I have added a third item which will define the color ( if < 30 ==> green / >30 ==> red )

Actually I'm trying to only use red color.

I have found a working example ,on how do do that. but it's based on non-time chart type.

I have tried to adapt it to my example but I get error in last step

ctx.bezierCurveTo(
  previous.controlPoints.outer.x,
  previous.controlPoints.outer.y,
  point.controlPoints.inner.x,
  point.controlPoints.inner.y,
  point.x,
  point.y
);

 "Uncaught TypeError: Cannot read property 'outer' of undefined",

Here a reproduction

 var canvas = document.getElementById('myChart'); let customLine = Chart.controllers.line.extend({ name: 'line', draw: function() { Chart.controllers.line.prototype.draw.apply(this, arguments); let datasetLength = this.chart.config.data.datasets.length; for (let i = 0; i < datasetLength; i++) { for (let j = 0; j < this.chart.config.data.datasets[i].data.length; j++) { var index = j; var datasetIndex = i; var hasValue = function(item) { return item.y !== null; }, previousPoint = function(point, collection, index) { return Chart.helpers.findPreviousWhere(collection, hasValue, index) || point; }; var ctx = this.chart.ctx; var dataset = this.chart.config.data.datasets[datasetIndex]; var pointsWithValues = Chart.helpers.where(dataset.data, hasValue); ctx.strokeStyle = 'red'; ctx.lineWidth = 3; ctx.beginPath(); var point = dataset.data[index]; ctx.moveTo(point.x, point.y); point = dataset.data[index + 1]; console.log(point) var previous = previousPoint(point, pointsWithValues, index + 1); ctx.bezierCurveTo( previous.controlPoints.outer.x, previous.controlPoints.outer.y, point.controlPoints.inner.x, point.controlPoints.inner.y, point.x, point.y ); ctx.stroke(); } } } }); Chart.controllers.customLine = customLine; var config = { "options": { "scales": { "xAxes": [ { "type": 'time', "time": { "unit": 'minute', "unitStepSize": 60, }, "distribution": 'linear', "bounds": 'ticks', "ticks": { "source": 'auto', "autoSkip": true, "stepSize": 10 } } ], }, }, "data": { "labels": ['2016-04-18T00:00:00Z', '2016-04-18T23:59:00Z'], "datasets": [ { "label": "line", "type": "customLine", "backgroundColor": "#00b", "borderColor": "#00b", //"yAxisID": "axis4", "borderWidth": 1, "fill": false, "data": [ {x:"2016-04-18T01:00:00Z", y:1,z:10}, {x:"2016-04-18T04:00:00Z", y:2,z:20}, {x:"2016-04-18T06:00:00Z", y:3,z:60}, {x:"2016-04-18T08:00:00Z", y:7,z:70}, {x:"2016-04-18T10:00:00Z", y:1,z:30}, {x:"2016-04-18T14:00:00Z", y:3,z:100} ] }, ] }, }; var myBarChart = Chart.Line(canvas, config);

 <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.0/Chart.bundle.min.js"></script> <canvas id="myChart" width="400" height="200"></canvas>

Answer 1

There's already an answer at another question which references a GitHub post which mentions a JSFiddle written in Chart.js 2.7.1 which can be updated to the latest 2.9.3 version without problems.

Credit to EgorOvechkin

Code:

var ctx = document.getElementById('myChart').getContext('2d');
//adding custom chart type
Chart.defaults.multicolorLine = Chart.defaults.line;
Chart.controllers.multicolorLine = Chart.controllers.line.extend({
  draw: function(ease) {
    var
      startIndex = 0,
      meta = this.getMeta(),
      points = meta.data || [],
      colors = this.getDataset().colors,
      area = this.chart.chartArea,
      originalDatasets = meta.dataset._children
        .filter(function(data) {
          return !isNaN(data._view.y);
        });

    function _setColor(newColor, meta) {
      meta.dataset._view.borderColor = newColor;
    }

    if (!colors) {
      Chart.controllers.line.prototype.draw.call(this, ease);
      return;
    }

    for (var i = 2; i <= colors.length; i++) {
      if (colors[i-1] !== colors[i]) {
        _setColor(colors[i-1], meta);
        meta.dataset._children = originalDatasets.slice(startIndex, i);
        meta.dataset.draw();
        startIndex = i - 1;
      }
    }

    meta.dataset._children = originalDatasets.slice(startIndex);
    meta.dataset.draw();
    meta.dataset._children = originalDatasets;

    points.forEach(function(point) {
      point.draw(area);
    });
  }
});

var chart = new Chart(ctx, {
    // The type of chart we want to create
    type: 'multicolorLine',

    // The data for our dataset
    data: {
        labels: ["January", "February", "March", "April", "May", "June", "July"],
        datasets: [{
            label: "My First dataset",
            borderColor: 'rgb(255, 99, 132)',
            data: [0, 10, 5, 2, 20, 30, 45],
            //first color is not important
            colors: ['', 'red', 'green', 'blue']
        }]
    },

    // Configuration options go here
    options: {}
});