code: private void set(Point3d[] x, Point3d[] y) {
  		this.x = x;
  		this.y = y;
  		rmsdCalculated = false;
  		transformationCalculated = false;
  	}
docs: Sets the two input coordinate arrays. These input arrays must be of equal
  length. Input coordinates are not modified.
  
  @param x
  3d points of reference coordinate set
  @param y
  3d points of coordinate set for superposition