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Dynamically update values of a chartjs chart


Question

I created an basic bar chart using chartjs and it works fine. Now I want to update the values on a time based interval. My problem is that after I created the chart, I do not know how to update its values correctly...

My code:

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);

in the test code, I am updating the values with datasets[0].data- is this the right way to do it? The problem with this is that everytime I call chart.Bar(), the values are reset to 0 then animated to the random value (like I am recreating the chart). This way, all animations are always from 0 to value which looks strange. I would expect that if I update a value from 50 to 10 the bar would go down to 10 from 50 and not setted to 0 then animated to 10.

I did not found anything in the docs about this... am I doing something wrong or this is impossible with this library?

2020/05/05
1
134
5/5/2020 10:02:36 AM

Accepted Answer

Update: Looks like chartjs has been updated (see comment below). There are some examples up that look very nice:

  1. Here's an example of updating a line chart using new data: http://jsbin.com/yitep/5/edit
  2. Here's how we can update existing data on a line chart: http://jsbin.com/yitep/4/edit

Original Post

As of Nov 2013, there seem to be very few options for updating charts.

There is a good example here (duplicated below) of adding new points to a line chart. Still kind of jumpy but not too bad. However, I think the effect probably depends on the chart you are using.

It does look like this is somewhere in the development pipeline. I don't see any indication of a release date yet though: https://github.com/nnnick/Chart.js/issues/13 [Closed as of Jul 26, 2014]

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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e(f,g),n+m*g,e(f,g)):b.lineTo(n+m*g,e(f,g));b.stroke();c.datasetFill?(b.lineTo(n+m*(a.datasets[f].data.length-1),p),b.lineTo(n,p),b.closePath(),b.fillStyle=a.datasets[f].fillColor,b.fill()):b.closePath();if(c.pointDot){b.fillStyle=a.datasets[f].pointColor;b.strokeStyle=a.datasets[f].pointStrokeColor;b.lineWidth=c.pointDotStrokeWidth;for(g=0;g<a.datasets[f].data.length;g++)b.beginPath(),b.arc(n+m*g,p-d*v(a.datasets[f].data[g],j,k),c.pointDotRadius,0,2*Math.PI,!0),b.fill(),b.stroke()}}},b)},L=function(a,
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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>
2019/05/06
101
5/6/2019 11:26:01 PM

The update() triggers an update of the chart. chart.update( )

.update(config)

Triggers an update of the chart. This can be safely called after updating the data object. This will update all scales, legends, and then re-render the chart. A config object can be provided with additional configuration for the update process.

update() can be safely called after updating values of one or more existing points within the the data object, rendering the changes in one animated render loop.

// 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();
2020/05/05

Here is how to do it in the last version of ChartJs:

setInterval(function(){
    chart.data.datasets[0].data[5] = 80;
    chart.data.labels[5] = "Newly Added";
    chart.update();
}

Look at this clear video

or test it in jsfiddle

2016/10/07

You also can use destroy() function. Like this

 if( window.myBar!==undefined)
     window.myBar.destroy();
 var ctx = document.getElementById("canvas").getContext("2d");
 window.myBar = new Chart(ctx).Bar(barChartData, {
     responsive : true,
 });
2014/12/03

You just need to change the chartObject.data.datasets value and call update() like this:

chartObject.data.datasets = newData.datasets;
chartObject.data.labels = newData.labels;
chartObject.update();
2018/01/18

Remove the canvas dom and add in again.

function renderChart(label,data){

    $("#canvas-wrapper").html("").html('<canvas id="storeSends"></canvas>');
    var lineChartData = {
        labels : label,
        datasets : [
            {
                fillColor : "rgba(49, 195, 166, 0.2)",
                strokeColor : "rgba(49, 195, 166, 1)",
                pointColor : "rgba(49, 195, 166, 1)",
                pointStrokeColor : "#fff",
                data : data
            }
        ]

    }
    var canvas = document.getElementById("storeSends");
    var ctx = canvas.getContext("2d");

    myLine = new Chart(ctx).Line(lineChartData, {
        responsive: true,
        maintainAspectRatio: false
    });
}
2014/11/27