紧急求教，matlab解四元微分方程的程序，谢谢

dx0/dt =20-0.15*x0*x1+0.8*0.05*x1+0.8*0.05*x2+0.8*0.05*x3
dx1/dt =x1*(-0.05+0.0265*0.15*x0-0.15*x2)
dx2/dt =x2*(-0.05+0.15*0.15*x1-0.15*x3)
dx3/dt ==x3*(-0.05+0.15*0.15*x2)

我想要的就是解析解，而且我也像你所说的做了，它显示 Error, (in dsolve/IC) The 'implicit' option is not available when giving Initial Conditions

先建立微分方程组子函数:
function f=yourfun(t,x)
f=zeros(4,1);
f(1) =20-0.15*x(1)*x(2)+0.8*0.05*x(2)+0.8*0.05*x(3)+0.8*0.05*x(4)
f(2) =x(2)*(-0.05+0.0265*0.15*x(1)-0.15*x(3))
f(3) =x(3)*(-0.05+0.15*0.15*x(2)-0.15*x(4))
f(4) =x(4)*(-0.05+0.15*0.15*x(3))
再调用
[T,X] = ode45(@yourfun,[0 10],[0 0.5 0 1]);
如果想直接看到结果可用
plot(T,X)

调用方法：[t,x] = ode45(@eqx,[0 0.2] ,[0 1 1.1 1.25])x的初始值写在一个矩阵里． 另外你的函数定义时k少一维k(4),我给你加了一个： function xdot = eqx(t,x); m = 0.5; alf = 0.15; k=[0.0265,0.1,0.15,0.12]; q=20; a=0.8; xdot = zeros(4,1); xdot(1) = q - alf * x(1) * x(2) + a*m*(x(1)+x(2)+x(3)+x(4)); xdot(2) = x(2) * (-m + k(2) * alf * x(1) - alf * x(3)); xdot(3) = x(3) * (-m + k(3) * alf * x(2) - alf * x(4)); xdot(4) = x(4) * (-m + k(4) * alf * x(3));