动态更新chartjs图表的值

Question

我使用 chartjs 创建了一个基本的条形图，它工作正常。现在我想在基于时间的间隔上更新值。我的问题是，创建图表后，我不知道如何正确更新其值…

我的代码：

var ctx = $("#myChart").get(0).getContext("2d");

var dts = [
    {
        fillColor: "rgba(220,220,220,0.5)",
        strokeColor: "rgba(220,220,220,1)",
        data: [0, 0, 0, 0, 0]
    }
];

var data = {
    labels: ["Core#1", "Core#2", "Core#3", "Core#4", "Total"],
    datasets: dts
};

var chart = new Chart(ctx);
chart.Bar(data);

//test code
setInterval( function () {
    data.datasets[0].data = [random(), random(), random(), random(), random()];
    chart.Bar(data);

},2000);

在测试代码中，我正在使用 datasets[0].data 更新值 - 这是正确的方法吗？问题在于，每次我调用 chart.Bar() 时，值都会重置为 0，然后动画为随机值（就像我正在重新创建图表一样）。这样，所有动画总是从 0 到看起来很奇怪的值。我希望如果我将一个值从 50 更新到 10，条形图将从 50 下降到 10，而不是设置为 0，然后动画到 10。

我在文档中没有找到任何关于此的内容……我做错了什么还是这个库不可能？

原文由 adanlif 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

更新： 看起来 chartjs 已经更新（见下面的评论）。上面有一些看起来很不错的例子：

1. 这是使用新数据更新折线图的示例：http: //jsbin.com/yitep/5/edit

2. 以下是我们如何更新折线图上的现有数据：http: //jsbin.com/yitep/4/edit

原帖

截至 2013 年 11 月，更新图表的选项似乎很少。

这里有一个 很好的例子（下面重复）向折线图添加新点。仍然有点跳动，但还不错。但是，我认为效果可能取决于您使用的图表。

看起来这确实在开发管道中的某个地方。不过，我还没有看到任何发布日期的迹象： https ://github.com/nnnick/Chart.js/issues/13 [截至 2014 年 7 月 26 日关闭]

JS

 $(document).ready(function(){
 var count = 10;
 var data = {
 labels : ["1","2","3","4","5", "6", "7", "8", "9", "10"],
 datasets : [
 {
 fillColor : "rgba(220,220,220,0.5)",
 strokeColor : "rgba(220,220,220,1)",
 pointColor : "rgba(220,220,220,1)",
 pointStrokeColor : "#fff",
 data : [65,59,90,81,56,45,30,20,3,37]
 },
 {
 fillColor : "rgba(151,187,205,0.5)",
 strokeColor : "rgba(151,187,205,1)",
 pointColor : "rgba(151,187,205,1)",
 pointStrokeColor : "#fff",
 data : [28,48,40,19,96,87,66,97,92,85]
 }
 ]
 }
 // this is ugly, don't judge me
 var updateData = function(oldData){
 var labels = oldData["labels"];
 var dataSetA = oldData["datasets"][0]["data"];
 var dataSetB = oldData["datasets"][1]["data"];

 labels.shift();
 count++;
 labels.push(count.toString());
 var newDataA = dataSetA[9] + (20 - Math.floor(Math.random() * (41)));
 var newDataB = dataSetB[9] + (20 - Math.floor(Math.random() * (41)));
 dataSetA.push(newDataA);
 dataSetB.push(newDataB);
 dataSetA.shift();
 dataSetB.shift(); };

 var optionsAnimation = {
 //Boolean - If we want to override with a hard coded scale
 scaleOverride : true,
 //** Required if scaleOverride is true **
 //Number - The number of steps in a hard coded scale
 scaleSteps : 10,
 //Number - The value jump in the hard coded scale
 scaleStepWidth : 10,
 //Number - The scale starting value
 scaleStartValue : 0
 }

 // Not sure why the scaleOverride isn't working...
 var optionsNoAnimation = {
 animation : false,
 //Boolean - If we want to override with a hard coded scale
 scaleOverride : true,
 //** Required if scaleOverride is true **
 //Number - The number of steps in a hard coded scale
 scaleSteps : 20,
 //Number - The value jump in the hard coded scale
 scaleStepWidth : 10,
 //Number - The scale starting value
 scaleStartValue : 0
 }

 //Get the context of the canvas element we want to select
 var ctx = document.getElementById("myChart").getContext("2d");
 var optionsNoAnimation = {animation : false}
 var myNewChart = new Chart(ctx);
 myNewChart.Line(data, optionsAnimation);

 setInterval(function(){
 updateData(data);
 myNewChart.Line(data, optionsNoAnimation)
 ;}, 2000
 );
 });

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HTML

 <html>
 <head>
 <script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
 </head>
 <body>
 <h1>Live Updating Chart.js</h1>

 <canvas id="myChart" width="400" height="150"></canvas>

 </body>
 </html>

原文由 doub1ejack 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 2

update() 触发图表更新。图表.更新（）

.update(config)

触发图表的更新。这可以在更新数据对象后安全地调用。这将更新所有比例、图例，然后重新呈现图表。 A config 对象可以提供更新过程的 附加配置。

update() 可以在更新数据对象中一个或多个现有点的值后安全地调用，在一个动画渲染循环中渲染变化。

 // update the first dataset's value of 'March' to be 50
myBarChart.data.datasets[0].bars[2].value = 50;

// animate update of 'March' from 90 to 50.
myBarChart.update();

原文由 Stig Husby 发布，翻译遵循 CC BY-SA 4.0 许可协议