CanvasJS line chart generation?

Question

I am busy trying to make a javascript chart for real-time data display. I found this CanvasJS API. The default code for that specific chart on their webpage is nice, but of course the part where they get the data, they have left the variable array empty and used a math randomize data function instead, in order that specific data will be randomly generated and used in the graph.

However I would like to full that array with my database data coming from a specific table I would like to use!

I have tried many things but if I implement my part, the graph won't display anymore. What am I doing wrong?

Here are the 3 codes I use:

The default code (just for comparison purpose):

<!DOCTYPE HTML>
<html>

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

        var dps = []; // dataPoints

        var chart = new CanvasJS.Chart("chartContainer",{
            title :{
                text: "Live Random Data"
            },          
            data: [{
                type: "line",
                dataPoints: dps 
            }]
        });

        var xVal = 0;
        var yVal = 100; 
        var updateInterval = 20;
        var dataLength = 500; // number of dataPoints visible at any point

        var updateChart = function (count) {
            count = count || 1;
            // count is number of times loop runs to generate random dataPoints.

            for (var j = 0; j < count; j++) {   
                yVal = yVal +  Math.round(5 + Math.random() *(-5-5));
                dps.push({
                    x: xVal,
                    y: yVal
                });
                xVal++;
            };
            if (dps.length > dataLength)
            {
                dps.shift();                
            }

            chart.render();     

        };

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

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

    }
    </script>
    <script type="text/javascript" src="/assets/script/canvasjs.min.js"></script>
</head>
<body>
    <div id="chartContainer" style="height: 300px; width:100%;">
    </div>
</body>
</html>

My own chart-code, based on the above code:

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title></title>
    <script src="jquery.js"></script>
    <script src="jquery.canvasjs.js" ></script>
    <script src="canvasjs.js"></script>

    <script type="text/javascript">
        $(document).ready(function () {

            $.getJSON("data.php", function (result) {

                var chart = new CanvasJS.Chart("chartContainer", {
                    data: [
                        {
                            dataPoints: result
                        }
                    ]
                });

                chart.render();
            });
        });
    </script>
</head>
<body>

    <div id="chartContainer" style="width: 800px; height: 380px;"></div>

</body>
</html>

and my data.php which displays the following output:

[{"x":"1","y":"5"},{"x":"2","y":"5"},{"x":"3","y":"4"},{"x":"4","y":"1"},{"x":"5","y":"8"},{"x":"6","y":"9"},{"x":"7","y":"5"},{"x":"8","y":"6"},{"x":"9","y":"4"},{"x":"10","y":"7"}]

 <?php
    //header('Content-Type: application/json');
    $con = mysqli_connect("localhost","root","","WebApplication");

    // Check connection
    if (mysqli_connect_errno($con))
    {
        echo "Failed to connect to DataBase: " . mysqli_connect_error();
    } 
    else
    {
    $data_points = array();

    $result = mysqli_query($con, "SELECT * FROM info");

    while($row = mysqli_fetch_array($result))
    {        
        $point = array("x" => $row['id'] , "y" => $row['acceleration']);

        array_push($data_points, $point);        
    }

        echo json_encode($data_points, 32); //define('JSON_NUMERIC_CHECK',32);   // Since PHP 5.3.3

    }
    mysqli_close($con);



    ?>

Hopefully you have enough info!

Thank you

Mieer

EDIT

I swapped the code from 'my own chart' -code for the following, based on @feedback-comment from: Anjali Jain

-->

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title></title>
    <script src="jquery.js"></script>
    <script src="jquery.canvasjs.js" ></script>
    <script src="canvasjs.js"></script>
    <script type="text/javascript" src="canvasjs.min.js"></script>


    <script type="text/javascript">
        $(document).ready(function () {

                $.getJSON("data.php", function (result) {

                var dataPoints = [];

                for (var i = 0; i <= result.length - 1; i++) {
                dataPoints.push({ x: Number(result[i].x), y: Number(result[i].y) });
                }

                var chart = new CanvasJS.Chart("chartContainer", {
                data: [
                {
                dataPoints: dataPoints
                }
                ]
                });

                chart.render();
                });
        });
    </script>
</head>
<body>

    <div id="chartContainer" style="width: 800px; height: 380px;"></div>

</body>
</html>

Yet, I still get nothing.

Anjali Jain Anjali Jain · Accepted Answer · 2015-05-25T14:09:28

CanvasJS requires x and y values to be numbers while you are passing strings directly. You can convert them to numbers as shown below

$.getJSON("data.php", function (result) {

    var dataPoints = [];

    for (var i = 0; i <= result.length - 1; i++) {
        dataPoints.push({ x: Number(result[i].x), y: Number(result[i].y) });
    }

    var chart = new CanvasJS.Chart("chartContainer", {
        data: [
        {
            dataPoints: dataPoints
        }
        ]
    });

    chart.render();
});

CanvasJS line chart generation?

1 Answers