MATLAB: Error using ODE45. Need Help Debugging

differential equationsode45

my m-file looks like
 function xp=F(t,x)
 xp=zeros(5,1); 
 m=1;
 w=1;
 h=.5;
 y=.01;
 xp(1)=-m*(w^2)*(x(2)^3)*(-(h*y)/(2*w*m))*24*x(3);
 xp(2)=x(1);
 xp(3)=2*w*x(4);
 xp(4)=-x(2)*w*(1+((12*x(2)*x(2))/(m*w*w)))*x(3)+w*x(5);
 xp(5)=-x(2)*w(1+((12*x(2)*x(2))/(m*w*w)))*x(4);
and when i set m,w,y,and h then run the code
 [t,x]=ode45('F',[0,10],[0,1,.5*((1+((12*x(2)*x(2))/(m*w*w)))^(-.5)),0,.5*((1+((12*x(2)*x(2))   
 /(m*w*w)))^(.5))]);
i get the errors
 ??? Index exceeds matrix dimensions.
 Error in ==> F at 11
 xp(5)=-x(2)*w(1+((12*x(2)*x(2))/(m*w*w)))*x(4);
 Error in ==> odearguments at 98
 f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.
 Error in ==> ode45 at 172
 [neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...

Best Answer

I can’t run your code because at the [t,x] = ode45(... line, I get:
Undefined function or variable "x".
that probably relates to referring to it in your initial conditions.
Otherwise, you likely need to ‘vectorize’ your code, using the dot operator, replacing * with .*, / with ./, and ^ with .^.
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