四阶龙格库塔法解微分方程，那位大哥会帮个忙吧

qiaoruijie

方程就像这样的y'=y-2x/y,x∈[0,0.6]
那个会帮帮忙啊，不胜感激，毕设急要啊！

xtxie

function R=rk4(f,a,b,ya,M)
%Input - f is the function entered as a string 'f'
% - a and b are the left and right endpoints
% - ya is the initial condition y(a)
% - M is the number of steps
%Output - R = [T' Y'] where T is the vector of abscissas
% and Y is the vector of ordinates
% NUMERICAL METHODS: Matlab Programs
% (c) 2004 by John H. Mathews and Kurtis D. Fink
% Complementary Software to accompany the textbook:
% NUMERICAL METHODS: Using Matlab, Fourth Edition
% ISBN: 0-13-065248-2
% Prentice-Hall Pub. Inc.
% One Lake Street
% Upper Saddle River, NJ 07458
h=(b-a)/M;
T=zeros(1,M+1);
Y=zeros(1,M+1);
T=a:h:b;
Y(1)=ya;
for j=1:M
k1=h*feval(f,T(j),Y(j));
k2=h*feval(f,T(j)+h/2,Y(j)+k1/2);
k3=h*feval(f,T(j)+h/2,Y(j)+k2/2);
k4=h*feval(f,T(j)+h,Y(j)+k3);
Y(j+1)=Y(j)+(k1+2*k2+2*k3+k4)/6;
end
R=[T' Y'];

xtxie

不知道你用什么写程序matlab的ode45函数就可以做，不过需要知道初始值

qiaoruijie

谢谢你啊，matlab也可以啊？