code: function () {
  		var series = this,
  			options = series.options,
  			xIncrement = series.xIncrement;
  
  		xIncrement = pick(xIncrement, options.pointStart, 0);
  
  		series.pointInterval = pick(series.pointInterval, options.pointInterval, 1);
  
  		series.xIncrement = xIncrement + series.pointInterval;
  		return xIncrement;
  	}
docs: Return an auto incremented x value based on the pointStart and pointInterval options.
  This is only used if an x value is not given for the point that calls autoIncrement.