解法matlab怎么求一阶常微分方程组（so 如何用matlab求下面一阶微分方程组的数值解
\u8bf7\u95ee\u5982\u4f55\u5b9e\u73b0matlab\u89e3\u4e00\u9636\u5fae\u5206\u65b9\u7a0b\u7ec4(\u7528\u5176\u81ea\u8eab\u547d\u4ee4\u5982ode45\u7b49\u600e\u4e48\u5199\u80fd\u8fd0\u884c\u51fa\u7ed3\u679c)\u5728Matlab\u4e0b\u8f93\u5165\uff1aedit\uff0c\u7136\u540e\u5c06\u4e0b\u9762\u4e24\u884c\u767e\u5206\u53f7\u4e4b\u95f4\u7684\u5185\u5bb9\uff0c\u590d\u5236\u8fdb\u53bb\uff0c\u4fdd\u5b58
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function dxdt=zhidao_rk4_5(t,x)
global a b c d r
x1=x(1);
x2=x(2);
x3=x(3);
x4=x(4);
dxdt=[
a*(x2-x1)+x4;
d*x1-x1*x3+c*x2;
x1*x2-b*x3;
x2*x3+r*x4;
];
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\u5728Matlab\u4e0b\u9762\u8f93\u5165\uff1a
global a b c d r
a=1;
b=2;
c=3;
d=4;
r=5;
t_end=10; %\u65f6\u95f4\u8ba1\u7b97\u7684\u7ec8\u70b9,\u5373\u7b97\u5230\u8fd9\u4e2a\u65f6\u95f4\u4e3a\u6b62
x0=[1;1;1;1]; %x\u7684\u521d\u59cb\u503c
[t,x]=ode45('zhidao_rk4_5',[0,t_end],x0);
\u7528matlab\u6c42\u4e0b\u9762\u4e00\u9636\u5fae\u5206\u65b9\u7a0b\u7ec4\u7684\u6570\u503c\u89e3
\u6b64\u5fae\u5206\u65b9\u7a0b\u53ef\u4ee5\u7528ode45\uff08\uff09\u51fd\u6570\u6c42\u7684\u5176\u6570\u503c\u89e3\u3002\u5176\u89e3\u8fc7\u7a0b\u4e3a
1题中x1=i,x2=s，则：
syms x1(t) x2(t)
lamda=0.5;u=0.1;
V = odeToVectorField(diff(x1) ==lamda*x1*x2-u*x2,diff(x2) ==-lamda*x1*x2+0.1)
M = matlabFunction(V,'vars', {'t','Y'})
%计算区间[0 1]，初值[0 0]
options = odeset('OutputFcn',@odeplot);
sol = ode45(M,[0 1],[0 0],options)
2题中x=x1,y=x2,z=x3,则：
syms x1(t) x2(t) x3(t)
V = odeToVectorField(diff(x1) ==-8/3*x1+x2*x3,diff(x2) ==-10*x2+10*x3,diff(x3)==-x1*x2+28*x2-x3)
M = matlabFunction(V,'vars', {'t','Y'})
%计算区间[0 1]，初值[0 0 1.0e-8]
options = odeset('OutputFcn',@odeplot);
sol = ode45(M,[0 4],[0 0 1.0e-8],options)
figure
x = linspace(0,4,100);
y = deval(sol,x,1:3);
plot(y(1,:),y(2,:))
title('x-y相图')
xlabel('x'),ylabel('y')
grid on
figure
plot(y(1,:),y(3,:))
title('x-z相图')
xlabel('x'),ylabel('z')
grid on
figure
plot3(y(1,:),y(2,:),y(3,:))
title('x-y-z相图')
xlabel('x'),ylabel('y'),zlabel('z')
grid on
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绛旓細V = odeToVectorField(diff(x1) ==-8/3*x1+x2*x3,diff(x2) ==-10*x2+10*x3,diff(x3)==-x1*x2+28*x2-x3)M = matlabFunction(V,'vars', {'t','Y'})璁＄畻鍖洪棿[0 1]锛屽垵鍊糩0 0 1.0e-8]options = odeset('OutputFcn',@odeplot);sol = ode45(M,[0 4],[0 0 1.0...
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