精细积分程序

代码说明：

在钟万勰院士最新书上的原代码 % Precise Integration Method clear; A=zeros(2); C=A; D=[0.5,0;0,1]; B=[-6,2;2,-4]; f0=[0;0;0;10]; f1=zeros(size(f0)); H=[A,D;B,C]; I=eye(size(H)); iH=inv(H);   tf=20; step=[2,0.5,0.1]; % different step size N=20; figure; hold; str=["o","x","b-"]; for jj=1:3   %PIM begin   dt=step(jj)/2^N;   Ta=H*dt+(H*dt)^2*(I+