Why do I get the error message "Index exceeds matrix dimensions."

The complete error message:

Index exceeds matrix dimensions.
Error in @(t,u,g,L)[u(2);-g/L*sin(u(1))]
Error in @(t,u)f(t,u,g,L)
Error in odearguments (line 87)
f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.

Error in ode45 (line 115)
    odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

The questioning is about a pendulum that have different starting values(10,30,....,170)of angle phi0. and I aren´t able to solv it. Thanks in advance :)

The code:

 L=0.1; g=9.82;
 phi0=linspace(10*pi/180,170*pi/180,9);
 f=@(t,u,g,L)[u(2); -g/L*sin(u(1))];
 tspan=linspace(0,1,200); 
 o=zeros(size(phi0));
 u0=[phi0;o];

 options=odeset('Events',@funevent);

 for i=1:1
    [t,U]=ode45(@(t,u)f(t,u,g,L),tspan,u0(i),options);
 end
subplot(1,2,1), plot(t,U(:,1),'g')
subplot(1,2,2), plot(U(:,1),U(:,2),'g')

Answer 1

[Abhisek Roy]

Hi Martin,

The error occurred as u0 provided to ode45 should be a [2,1] vector as the dynamics has two states. So change u0(i) to u0(:,i) and you should be able to integrate it. Also you have not defined funevent function, so define it before you run again, or you can remove it also.