code: function (x, y, r) {
  		var circle = this.symbol('circle');
  		if (isObject(x)) {
  			r = x.r;
  			y = x.y;
  			x = x.x;
  		}
  		circle.isCircle = true; // Causes x and y to mean center (#1682)
  		circle.r = r;
  		return circle.attr({ x: x, y: y });
  	}
docs: Create and return a circle element. In VML circles are implemented as
  shapes, which is faster than v:oval
  @param {Number} x
  @param {Number} y
  @param {Number} r