text: var chart = c3.generate({
      data: {
          columns: [
              ['data1', 30, 200, 100, 400, 150, 250],
              ['data2', 130, 100, 140, 200, 150, 50]
          ],
          type: 'bar'
      }
  });
  
  setTimeout(function () {
      chart.transform('area-spline', 'data1');
  }, 1000);
  
  setTimeout(function () {
      chart.transform('area-spline', 'data2');
  }, 2000);
  
  setTimeout(function () {
      chart.transform('bar');
  }, 3000);
  
  setTimeout(function () {
      chart.transform('area-spline');
  }, 4000);
  