How can I increase the array elements of the optimization variable?

Hi all,

I am trying to run a dynamic optimization script, and I get the error message:

    Index exceeds the number of array elements (1).
    
    Error in myModel (line 3)
        dxdt(1)= -2.85.*(1/((1/k(4))+(1/k(1))).*k(3).*x(2)*x(1).*(1-(k(2).*x(1))/(1+(k(2).*x(1)))));
    
    Error in myObj>@(t,x)myModel(t,x,k) (line 24)
    [t,x] = ode15s(@(t,x)myModel(t,x,k),time,x0);
    
    Error in odearguments (line 90)
    f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.
    
    Error in ode15s (line 150)
        odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);
    
    Error in myObj (line 24)
    [t,x] = ode15s(@(t,x)myModel(t,x,k),time,x0);
    
    Error in fminsearch (line 200)
    fv(:,1) = funfcn(x,varargin{:});
    
    Error in DynamicOptimization (line 3)
    k = fminsearch('myObj',0.05);

On another code, I used:

    sol = zeros(1,numel(t));

to resolve the error of:

Index exceeds the number of array elements (1).

In the attached example, I don't know how to do it.

Please help.