public void addDataPoints(String group, DataPoints dp)
	{
		if (dp==null || dp.isEmpty()) return;

		group = group.toLowerCase();
		if (!this.m_PointsSet.containsKey(group))
		{
			this.m_PointsSet.put(group, dp);
		} else
		{
			for (DataPoint p: dp)
				this.m_PointsSet.get(group).addPoint(p.getX(), p.getY());
		}
		
		// calculate min max values
		calculateMinMax();
	}