an class="keyword">if</span> n==3,
0081       xp=-x(1:nn-3)+x(2:nn-2);
0082       yp=-y(1:nn-3)+y(2:nn-2);    
0083       xpp=2*x(1:nn-3)-5*x(2:nn-2)+4*x(3:nn-1)-x(4:nn);
0084       ypp=2*y(1:nn-3)-5*y(2:nn-2)+4*y(3:nn-1)-y(4:nn);
0085       vor=0;nach=3;
0086   <span class="keyword">end</span>
0087   <span class="keyword">if</span> n==4,
0088       xp=(-3*x(2:nn-5)-10*x(3:nn-4)+18*x(4:nn-3)-6*x(5:nn-2)+x(6:nn-1))/12;
0089       yp=(-3*y(2:nn-5)-10*y(3:nn-4)+18*y(4:nn-3)-6*y(5:nn-2)+y(6:nn-1))/12;
0090     