[爆炸] 昨天講的 bifurcation matlab file

[ANUBISANKH (Pourquoi？)]

(1) 先開一個 .m file 建立 function (他會直接要求你存成 hysterisis.m):


function dydt=hysterisis(t,x,u)
global u;
dydt=[u*x+x^3-x^5];


(2) 建立執行檔，一樣開一個 .m file:

clear all;

global u;

for i=1:100

    % setting the range of parameter "u"
    u=0.01*(i-50);

    % different initial conditions
    x0=[2.15];
    y0=[0.04];
    a0=[-2.15];
    b0=[-0.04];

    % solving odes by ode45
    [t,x]=ode45(@hysterisis,0:0.1:10,x0);
    [t,y]=ode45(@hysterisis,0:0.1:10,y0);
    [t,a]=ode45(@hysterisis,0:0.1:10,a0);
    [t,b]=ode45(@hysterisis,0:0.1:10,b0);

    % defining the 100th step calculation of x as x*
    X(i)=x(100);
    Y(i)=y(100);
    A(i)=a(100);
    B(i)=b(100);

    % redefining the parameter "u" as "u(i)"
    U(i)=u;

end

subplot(2,2,1),plot(U,X)
ylabel('x*')
xlabel('u')
subplot(2,2,2),plot(U,Y)
ylabel('x*')
xlabel('u')
subplot(2,2,3),plot(U,A)
ylabel('x*')
xlabel('u')
subplot(2,2,4),plot(U,B)
ylabel('x*')
xlabel('u')


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先這樣啦，試試看就好。

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