Not Sure How to Fix Error where I Define Function

Hello,

I am not sure how to fix my function in my script.

Attached is a sample of my code:

clc; clear all;

ti = 0;  
tf = 15; 

global I11 I22 I33 Mx My Mz w10 w20 w30 eps10 eps20 eps30 eps40...
       C110 C120 C130 C210 C220 C230 C310 C320 C330 IC K0

I11 = 160;  
I22 = 400;
I33 = 400;

Mx = 0;
My = 0;
Mz = 45;

w10 = 2;
w20 = -1;
w30 = 1;

eps10 = 0;
eps20 = 0;
eps30 = 0;
eps40 = 1;

K0 = eps10^2+eps20^2+eps30^2+eps40^2;

C110 = 1-2*eps20^2-2*eps30^2;
C120 = 2*(eps10*eps20-eps30*eps40);
C130 = 2*(eps30*eps10+eps20*eps40);
C210 = 2*(eps10*eps20+eps30*eps40);
C220 = 1-2*eps30^2-2*eps10^2;
C230 = 2*(eps20*eps30-eps10*eps40);
C310 = 2*(eps30*eps10-eps20*eps40);
C320 = 2*(eps20*eps30+eps10*eps40);
C330 = 1-2*eps10^2-2*eps20^2;

IC = [w10 w20 w30...
      eps10 eps20 eps30 eps40...
      C110 C120 C130 C210 C220 C230 C310 C320 C330];

opts  = odeset('RelTol', 1*10^(-10),'AbsTol', 1*10^(-10)); 
[t, y] = ode45(@(t,y) DynEqn1(t,y,I11,I22,I33,Mx,My,Mz), [ti tf], IC, opts);

N = sqrt(sum(y(:,4:7).^2,2));  


kap = acosd(1-2*y(:,5)^2-2*y(:,7)^2);

phi1 = acosd((2*(y(:,4)*y(:,5)+y(:,6)*y(:,7)))/sind(kap));
phi2 = asind((2*(y(:,6)*y(:,4)-y(:,5)*y(:,7)))/sind(kap));
if phi1==phi2
    phi = phi1;
elseif phi1==180-phi2
    phi = phi1;
elseif -phi1==phi2
    phi = -phi1;
elseif -phi1==180-phi2
    phi = -phi1;
else
    disp('Something is wrong with phi')

figure (1)
plot(t,phi)

figure (2)
plot(t,kap)

figure (3)
plot(y(:,11),y(:,14))

function soln = DynEqn1(t,y,I11,I22,I33,Mx,My,Mz)
w1 = y(1);
w2 = y(2);
w3 = y(3);

eps1 = y(4);
eps2 = y(5);
eps3 = y(6);
eps4 = y(7);

C11 = y(8);
C12 = y(9);
C13 = y(10);
C21 = y(11);
C22 = y(12);
C23 = y(13);
C31 = y(14);
C32 = y(15);
C33 = y(16);

w1_dot = (Mx - w2*w3*(I33-I22))/I11;
w2_dot = (My - w1*w3*(I11-I33))/I22;
w3_dot = (Mz - w1*w2*(I22-I11))/I33;

eps1_dot = .5*(w1*eps4-w2*eps3+w3*eps2);
eps2_dot = .5*(w1*eps3+w2*eps4-w3*eps1);
eps3_dot = .5*(-w1*eps2+w2*eps1+w3*eps4);
eps4_dot = -.5*(w1*eps1+w2*eps2+w3*eps3);

C11_dot = C12*w3-C13*w2;
C12_dot = C13*w1-C11*w3;
C13_dot = C11*w2-C12*w1;
C21_dot = C22*w3-C23*w2;
C22_dot = C23*w1-C21*w3;
C23_dot = C21*w2-C22*w1;
C31_dot = C32*w3-C33*w2;
C32_dot = C33*w1-C31*w3;
C33_dot = C31*w2-C32*w1;


soln = [w1_dot; w2_dot; w3_dot; ...
        eps1_dot; eps2_dot; eps3_dot; eps4_dot; ...
        C11_dot; C12_dot; C13_dot; C21_dot; C22_dot; C23_dot; C31_dot; C32_dot; C33_dot];

end

I get this at the line where I begin the function:

Function definitions are not permitted in this context.

I double checked that I had the correct number of initial conditions that match the number of solutions I defined.

Furthermore, this code was basicaly just an edit from a previous code of mine, where all I did was add C11 through C33 and C11_dot through C33_dot in the function.

I also defined some more variables and plotted different things, but none of that is inside the function, so I don't think that is the issue.

Any help is appreciated, thank you.

Answer 1

[the cyclist]

Functions need to be defined in their own files. They cannot be specified in the command window or in scripts.

Put the function definition portion:

function soln = DynEqn1(t,y,I11,I22,I33,Mx,My,Mz)
   ...
end

into a file named DynEqn1.m.

There may be other errors, but that is the specific problem that is giving that error message.

[Stephen23]

" They cannot be specified ... in scripts."

Since R2016b: https://www.mathworks.com/help/matlab/matlab_prog/local-functions-in-scripts.html