Home forums Using CanvasJS How to draw an array value and repeat at the end, running real time chart Reply To: How to draw an array value and repeat at the end, running real time chart

#4886

Sunil Urs
Keymaster

I just tried your code and it is not updating at all. So I had to make several changes to make it update the data. Hence am not sure if this is what you expected. Below is a working code.

<script type="text/javascript">
        window.onload = function () {

            var dps = []; // dataPoints
            var instance = (new Date()).getTime();
            var chart = new CanvasJS.Chart("chartContainer", {
                title: {
                    text: "Live SpO2 Data"
                },
                axisX: {
                    title: "Time",
                    valueFormatString: "hh:mm:ss"
                },

                axisY: {
                    title: "%SpO2",
                },
                data: [{
                    type: "spline",
                    xValueType: "dateTime",
                    dataPoints: dps
                }]
            });

            var yVal = [0.02, 0.02, 0.02, 0.02, 0.05, 0.07, 0.06, 0.09, 0.06, -0.2, 0.9, 0.5, -0.1, 0.02, 0.02, 0.04, 0.1, 0.08, 0.03, 0.02, 0.02, 0.02, 0.02, 0.02];
            var updateInterval = 1000;
            var maxDataLength = yVal.length; // number of dataPoints after which the series shifts
            var time = new Date();
            var updateCount = 0;

            var updateChart = function (count) {

                count = count || 1;

                for (var j = 0; j < count; j++) {
                    time.setSeconds(time.getSeconds() + 1);

                    dps.push({
                        x: time.getTime(),
                        y: yVal[updateCount % yVal.length]
                    });

                    updateCount++;

                    if (dps.length > maxDataLength) {
                        dps.shift();
                    }
                }
                

                chart.render();

            };

            // generates first set of dataPoints
            updateChart(maxDataLength);

            // update chart after specified time.
            setInterval(function () { updateChart();}, updateInterval);

        }

    </script>