code: public void emphasizePoint( int index )
  	{
  		if( dots == null || dots.length < (index - 1) )
  			return; // impossible !
  
  		// if no change, nothing to do
  		if( emphasizedPoint == index )
  			return;
  
  		// de-emphasize the current emphasized point
  		if( emphasizedPoint >= 0 )
  		{
  			dots[emphasizedPoint].attr( "r", dotNormalSize );
  
  			emphasizedPoint = -1;
  		}
  
  		if( index >= 0 )
  		{
  			dots[index].attr( "r", dotBigSize );
  
  			emphasizedPoint = index;
  		}
  	}
docs: index < 0 means that we emphasize no point at all