Time-dependent immunity and drug resistant SIR model

I have to solve this SIR model with Euler's forward. But my teacher said that it is wrong with my graph. Can anyone help me ?

Here is my code

%initial values

S(1)= 1;

I_1(1)= 0;

I_2 (1) = 0;

R(1)= 0;

tMax= 50;

dt = 0.01;

time_vector = 0:dt:tMax;

nIterations = length(time_vector);

t= 0:dt:tMax;

v= 0.0024;

tau = 0.6;

u= 0.8;

h= 0.5;

rho = 0.8;

R = 0.2;

r= re(R,v,t);

b = BetaL(h,tau);

n=0 ;

for i = time_vector

n = n+1;

S(n+1)= S(n)-dt*h*S(n)+dt*rho*I_1(n)+dt*b.*R(n);

I_1(n+1) =I_1(n)+ dt*(1-u)*S(n) - dt*rho*I_1(n) - dt*u*h*I_1(n);

I_2(n+1) =I_2(n)+ dt*u*h*S(n) + dt*u*h*I_1(n) - dt*r(n)*I_2(n);

R(n+1)= R(n) + dt*r(n)*I_2(n) - dt*b*R(n);

end

hold on

plot (t,S(1:end-1),'-r');

plot (t,I_1(1:end-1),'-b');

plot (t,I_2(1:end-1),'.b');

plot (t,R(1:end-1),'-g');

xlabel ('t');

ylabel ('population');

title ('Drug resistant model');

legend ('S','I_1','I_2','R');

[Aquatris]

What is BetaL function?

In the line with "S(n+1) = ..." you do not use the b(h)

In the line "I2(n+1) = ..." you are missing (1-exp(-vt^2).

In the line "R(n+1) = ..." you are missing (1-exp(-vt^2)

Answer 1

[ME]

Assuming you have your BetaL and re functions setup correctly then there are the errors listed in the comment from Aquatris but you are also missing a multiple "h" in the I_1(n+1) equation.

Your equations at the bottom of your question also state that =0.2 but you appear to have set R=0.2 instead and then defined a function r(n) instead of using .

If fixing those items doesn't help then I think you might need to give some more information as to what the BetaL and re functions are supposed to be.

[HAAAAH]

thank you. i fixed it