anchor.diff:      } else {
         color = dataPoint['color'];
       }
  -    // Update maximum values.
  -    maxX = dataPoint['point'][0] > maxX ? dataPoint['point'][0] : maxX;
  -    maxY = dataPoint['point'][1] > maxY ? dataPoint['point'][1] : maxY;
   
       // Create the circle element
       svg.CircleElement point = new svg.CircleElement();
       point.attributes = {
  -      'cx': '${dataPoint['point'][0]}',
  -      'cy': '${dataPoint['point'][1]}',
  +      'cx': '${dataPoint['point'][0] - minX.toInt()}',
  +      'cy': '${dataPoint['point'][1] - minY.toInt()}',
         'r': '2',
         'fill': color,
       };
  
positive.code:     assert(dataPoint['point'].length == 2);
      assert(dataPoint.containsKey('value'));
      assert(dataPoint.containsKey('color'));
      // Color can be an int (the format of the image package for Dart)
      // or a (hex) string.
      String color;
  
negative.code: 
    // Record maximum values of x and y which represent the width and height for
    // background necessary for zooming and panning.
    num minX, maxX, minY, maxY;
    minX = minY = double.INFINITY;
    maxX = maxY = double.NEGATIVE_INFINITY;
  
    for (Map dataPoint in data) {
  