p=ypp-(y(2:nn-1)-y(1:nn-2))./(t(2:nn-1)-t(1:nn-2));
0072       xpp=ypp./(t(3:nn)-t(1:nn-2))/2;
0073   <span class="keyword">end</span>
0074   <span class="keyword">if</span> n==2,
0075       xp=(x(1:nn-4)-8*x(2:nn-3)+8*x(4:nn-1)-x(5:nn))/12;
0076       yp=(y(1:nn-4)-8*y(2:nn-3)+8*y(4:nn-1)-y(5:nn))/12;
0077       xpp=(-x(1:nn-4)+16*x(2:nn-3)-30*x(3:nn-2)+16*x(4:nn-1)-x(5:nn))/12;
0078       ypp=(-y(1:nn-4)+16*y(2:nn-3)-30*y(3:nn-2)+16*y(4:nn-1)-y(5:nn))/12;
0079   <span class="keyword">end</span>
0080   <sp