MATLAB: ERROR USING A FUNCTION INSIDE ODE FUNCTION

numerical integrationode45

I am trying to solve a 2nd order differential equation which involves invoking a function defined in the main code from inside another function. However, I am ending up with an error that says
    Undefined function or variable 'partial_psi_x'.
    Error in P3>odefunc (line 103)
    dudt = -partial_psi_x(x,y,z);
    Error in odearguments (line 90)
    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);
    Error in P3 (line 91)
    [t,s] = ode45(@odefunc, tspan, s0);
Relevant piece of code is as follows:
    partial_psi_x = partial_psi_b_x + partial_psi_d_x + partial_psi_h_x;
    partial_psi_y = partial_psi_b_y + partial_psi_d_y + partial_psi_h_y;
    partial_psi_z = partial_psi_b_z + partial_psi_d_z + partial_psi_h_z;
    partial_psi_x = matlabFunction(partial_psi_x);
    partial_psi_y = matlabFunction(partial_psi_y);
    partial_psi_z = matlabFunction(partial_psi_z);
   % ODE
   tstart = 0;
   tstop = 2*pi;
   tspan=tstart:tstop;
   s0=[-R0;0;0;0;V0;0];
   [t,s] = ode45(@odefunc, tspan, s0);
   function dsdt = odefunc(t,s)
   x = s(1);
   y = s(2);
   z = s(3);
   u = s(4);
   v = s(5);
   w = s(6);
   dxdt = u;
   dydt = v;
   dzdt = w;
   dudt = -partial_psi_x(x,y,z);
   dvdt = -partial_psi_y(x,y,z);
   dwdt = -partial_psi_z(x,y,z);
   dsdt = [dxdt;dydt;dzdt;dudt;dvdt;dwdt];
   end
where partial_psi_x, partial_psi_y and partial_psi_z are function handles (after using MatlabFunction) to partial derivatives of a function psi in terms of x, y and z. I have checked until the point of obtaining the three function handles and they seem to work without any issues. However, when I try to access these functions from inside odefunc, I get error as mentioned above. I am fairly new to numerical integration technique in MATLAB but have tried to look up a similar approach of using functions inside an ode solver but could not find any solution. Any help on the issue will be highly appreciated.

Best Answer

You should pass in those function handles as extra parameters.
http://www.mathworks.com/help/matlab/math/parameterizing-functions.html
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