<canvas id="canvasMyID" height="300" width="400"></canvas>
<p>
  <input type="button" value="ajax load data0.txt" 
         onclick="$('#canvasMyID').jQchart('./data0.txt')">
  <input type="button" value="ajax load data1.txt" 
         onclick="$('#canvasMyID').jQchart('./data1.txt')">
  <input type="button" value="ajax load data2.txt" 
         onclick="$('#canvasMyID').jQchart('./data2.txt')">
</p>