code: public double[][] getPositionsAsArray(){
  		double[][] posAsArr = new double[size()][3];
  		for(int i = 0; i < size(); i++){
  			if(get(i)!=null){
  				posAsArr[i][0] = get(i).x;
  				posAsArr[i][1] = get(i).y;
  				posAsArr[i][2] = get(i).z;
  			}
  			else{
  				posAsArr[i] = null;
  			}
  		}
  		return posAsArr;
  	}
docs: Converts the positions to a 2D double array
  @return 2d double array [i][j], i=Time index, j=coordinate index