Chartjs-Creating a heart rate monitor

You could use 2 series and just swap in the points. You might need to interpolate between points to smoothen out the animation.

I’ve used linear interpolation, but for a smoother curve you could probably use something else, but I believe if you have actual data, linear interpolation would work fine.

function getActualData() {
    var actualData = []
    for (var m = 0; m < 20; m++)
        actualData.push(45 + parseInt(Math.random() * 35))
    return actualData;
}


var ANIMATIONSTEPS = 200;

var myLineChart;
var labels;
var animationStep;
setInterval(function () {
    if (myLineChart === undefined) {
        var actualData = getActualData();

        // if we have only a few data points interpolate to fill out enough points to make the animation smooth
        var interpolationSteps = Math.ceil(ANIMATIONSTEPS / actualData.length);
        labels = []
        var data = []
        var blankData = []
        for (var i = 0; i < (actualData.length - 1); i++) {
            labels.push('')
            data.push(actualData[i])
            blankData.push(null)

            // push interpolation
            var difference = actualData[i + 1] - actualData[i];
            var interpolationStep = 1 / interpolationSteps;
            for (var j = 1; j < interpolationSteps; j++) {
                labels.push('')
                data.push(actualData[i] + difference * Chart.helpers.easingEffects["linear"](j * interpolationStep));
                blankData.push(null)
            }
        }
        labels.push('')
        data.push(actualData[i])
        blankData.push(null)

        var data = {
            labels: labels,
            datasets: [
                {
                    strokeColor: "rgba(243, 118, 27, 1)",
                    data: blankData
                },
                {
                    strokeColor: "transparent",
                    data: data
                }
            ]
        };

        var ctx = document.getElementById("myChart").getContext("2d");
        myLineChart = new Chart(ctx).Line(data, {
            animation: false,
            datasetFill: false,
            pointDot: false,
            datasetStrokeWidth: 5,
            showTooltips: false,
            scaleOverride: true,
            scaleSteps: 12,
            scaleStepWidth: 5,
            scaleStartValue: 30,
            scaleShowVerticalLines: false,
            scaleShowLabels: false,
        });

        animationStep = 0;
    }

    // the actual animation
    myLineChart.datasets[0].points[animationStep].value = myLineChart.datasets[1].points[animationStep].value
    myLineChart.update();
    animationStep++;

    // start new cycle
    if (animationStep >= labels.length) {
        myLineChart.destroy();
        myLineChart = undefined;
    }
}, 10)

Fiddle – http://jsfiddle.net/t795k4j3/