Doughnut Chart in chart.js

HTML

<script src="http://www.chartjs.org/assets/Chart.js"></script>
<canvas id="myChart" width="400" height="400"></canvas>

JavaScript

var data = [{"grade": "Grade K", "studentId": 1}, 
            {"grade": "Grade 1", "studentId": 2}, 
            {"grade": "Grade 2", "studentId": 3}, 
            {"grade": "Grade 3", "studentId": 4}
           ];

    var options = {
        animation: true
    };

    //Get the context of the canvas element we want to select
    var c = $('#myChart');
    var ct = c.get(0).getContext('2d');
    var ctx = document.getElementById("myChart").getContext("2d");
    /*************************************************************************/
    myNewChart = new Chart(ct).Doughnut(data, options);