system of differential equations, function call

I have written the following code. Trying to simulate the zombie apocalypse. There might be something wrong with my ode45, and it might be something wrong with my function. I'd be grateful if someone could help me out :)

(I'm not quite sure about the 'options' either...)

%%%%%%%%%%%%%%%%%%%%%%%%%

syms x t;

tspan = [1 100];

options = odeset('RelTol',1e-6,'AbsTol',1,'InitialStep',tspan);

a = 1.4e-6;

b = 3.1e-8;

bd = 5.6e-16;

d = 2.8e-8;

i = 2.6e-6;

n = 1.4e-6;

r = 2.8e-7;

qi = 2.7e-6;

qz = 2.7e-6;

dq = 2.8e-5;

H0 = (b-d)/bd;

[t1,x1]=ode45(@(t,x) zombie1(t, x, a, b, bd, d, i, n, r),tspan,[H0,0,0,0]',options);

%%%%%%%ERROR MESSAGE%%%%%%%

zombie = 4×1

-0.0000

0

0

0.1500

Output argument "zombie1" (and maybe others) not assigned during call to "zombie1".

Error in MS_Ov3 (line 43)

[t1,x1]=ode45(@(t,x) zombie1(t, x, a,b,bd,d,i,n,r),tspan,[H0,0,0,0]',options);

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);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

[t2,x2]=ode45(@(t,x) zombie2(t, x, a,b,bd,d,i,n,r,qi,qz,dq),tspan,[H0,0,0,0,0]',options);

figure(1)

subplot(1,2,1);

grid on;

plot(t1, x1, '-o');

title('Zombieapokalypse');

subplot(1,2,2);

grid on;

plot(t2, x2, '-o');

title('Zombieapokalypse m karantene');

%%%%%%%%%%%%%%%%%%%%%%%%

The code is written in matlab livescript, the functions are in different scripts, same path.

Here's the function: (Second one is similar)

%%%%%%%%%%%%%%%%

function zombie1 = zombie(t, x, a,b,bd,d,i,n,r)

zombie = [b*x(1) - d*x(1) - i*x(1)*x(3) - bd*x(1)^2;

i*x(1)*x(3) - a*x(2) - d*x(2);

a*x(2) - n*x(1)*x(3) + r*x(4);

d*(x(1) - x(2)) + n*x(1)*x(3) - r*x(4)]

end

Answer 1

[Star Strider]

Try this:

function zombie1 = zombie(t, x, a,b,bd,d,i,n,r)
 
     zombie1 = [b*x(1) - d*x(1) - i*x(1)*x(3) - bd*x(1)^2;
            i*x(1)*x(3) - a*x(2) - d*x(2);
            a*x(2) - n*x(1)*x(3) + r*x(4);
            d*(x(1) - x(2)) + n*x(1)*x(3) - r*x(4)];
end

Also, there is no ‘zombie2’ function in the code you posted, and there are too many input arguments to ‘zombie’ in the second ode45 call. You need to fix those, as well as the problem with the odeset call.