Solving two equations with ODE45

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Sergio Manzetti
Sergio Manzetti 2018-4-4
编辑： Sergio Manzetti 2018-4-4
Hi, I used the following command to solve one ODE
fun = @(x,y)[y(2);y(3);(y(1)*(1-x^2))];
y0 = [1 0 8]; %y, y', y''
xspan = [-3 3];
[X,Y] = ode45(fun,xspan,y0);
plot(X,Y(:,1)),,% X,Y(:,2),X,Y(:,3),X,Y(:,1).* (2 + X .^ 2));
However, I would like to solve this pair of equations instead of the given "fun":
How do I add two equations in the fun line?
Thanks!

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采纳的回答

Torsten
Torsten 2018-4-4
fun=@(x,y)[y(2);y(3);-(1+x^2)*y(4);y(5);y(6);(1+x^2)*y(1)]; %psi2,psi2',psi2'',psi1,psi1',psi1''
Best wishes
Torsten.
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Sergio Manzetti
Sergio Manzetti 2018-4-4
编辑：Sergio Manzetti 2018-4-4
Thanks, following your link I used a new y0 and got a result, but plot only plots one form.
fun=@(x,y)[y(2);y(3);-(1+x^2)*y(4);y(5);y(6);(1+x^2)*y(1)]; %psi2,psi2',psi2'',psi1,psi1',psi1''
y0 = [1 0 8 1 0 8]; %y, y', y''
xspan = [-3 3];
[X,Y] = ode45(fun,xspan,y0);
plot(X,Y(:,1)), X,Y(:,2),X,Y(:,3),X,Y(:,1), '-o',X,Y(:,2), X,Y(:,2),X,Y(:,3),X,Y(:,1);
What is wrong in the plot section really?
Sergio Manzetti
Sergio Manzetti 2018-4-4
编辑：Sergio Manzetti 2018-4-4
Hi Torsten, I edited this finally:
fun=@(x,y)[y(2);y(3);-(1+x^2)*y(4);y(5);y(6);(1+x^2)*y(1)]; %psi2,psi2',psi2'',psi1,psi1',psi1''
y0 = [1 0 8 1 0 8]; %y, y', y''
xspan = [-3 3];
[X,Y] = ode45(fun,xspan,y0);
plot(X,Y(:,1)), X,Y(:,2),X,Y(:,3),X,Y(:,1);
So it shows a plot. But this plot is identical to the plot of only one function present in the command (remove the second function and decrease to three dimensions, and it is the same plot).
Is that correct? I would have expected a different solution.

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KSSV
KSSV 2018-4-4

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