# Why doesn't M2 function get called? Could somebody please explain what this error is and how to fix it?

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cindyawati cindyawati el 17 de Jun. de 2023
Comentada: cindyawati cindyawati el 20 de Jun. de 2023
I have function for M2
function M2 =fRK4M2(M1,M2)
M1=10;
M2=0;
mu_2=10^-3;
K1= 10^-4;
K2=5*10^-4;
M2 = (K1*M1*M1)-(K2*M1*M2)-(mu_2*M2);
This is my M1 function
function M1 =fRK4M1(M1,M2,M3,O,P)
delta=50;
K1= 10^-4;
Ko=0.1;
n=3;
Oa=10;
Pa=100;
mu_1=10^-3;
K2=5*10^-4;
K3=10^-3;
gamma=75;
M1=(delta*M1*(1-(M1/gamma))-2*K1*M1*M1-M1*(K2.*M2)-((Oa-n)*K3*M1*M3)-((Pa-Oa)*Ko*M1*O)-(mu_1*M1));
And this is my main function
clc;clear;
%input for time
t(1)=0;
dt=0.1; %time interval
t=0:dt:100; %time span
%input empty array
T=zeros(length(t),1); %empty array for t
M1=zeros(length(t),1); %empty array for M1
M2=zeros(length(t),1); %empty array for M2
for j = 1:length((t))
T(j+1)=T(j)+dt;
M1(j+1)= M1(j)+1./(1+exp(-T(j)));
k1M2 = dt*fRK4M2(M2(j),M1(j));
k2M2 = dt*fRK4M2(M2(j)+k1M2/2,M1(j)+k1M2/2);
k3M2 = dt*fRK4M2(M2(j)+k2M2/2,M1(j)+k2M2/2);
k4M2 = dt*fRK4M2(M2(j)+k3M2,M1(j)+k3M2/2);
M2(j+1) = M2(j)+1/6*(k1M2+2*k2M2+2*k3M2+k4M2);
k1M1= dt*fRK4M1(M1(j),M2(j));
k2M1= dt*fRK4M1(M2(j)+k1M2/2,M1(j)+k1M1/2);
k3M1= dt*fRK4M1(M2(j)+k2M2/2,M1(j)+k2M1/2);
k4M1= dt*fRK4M1(M2(j)+k3M2/2,M1(j)+k3M1/2);
M1(j+1) = M1(j)+(1/6*(k1M1+(2*k2M1)+(2*k3M1)+k4M1));
end
the results I get are not as desired, please someone tell me my fault adn how to fix it. Thanks
##### 2 comentariosMostrar NingunoOcultar Ninguno
Torsten el 18 de Jun. de 2023
So the task of your code is to solve the system of differential equations
dM1/dt = (delta*M1*(1-(M1/gamma))-2*K1*M1*M1-M1*(K2.*M2)-((Oa-n)*K3*M1*M3)-((Pa-Oa)*Ko*M1*O)-(mu_1*M1))
dM2/dt = (K1*M1*M1)-(K2*M1*M2)-(mu_2*M2)
?
Since your code has so many errors, I suggest you use ODE45 for the solution.
cindyawati cindyawati el 18 de Jun. de 2023
Editada: cindyawati cindyawati el 18 de Jun. de 2023
thank you for response @Torsten yes my code to solve the system of differential equation. If I use Runge Kutta orde 4th is it possible?

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### Respuestas (1)

Lakshya el 17 de Jun. de 2023
Hi,
The code you provided initializes M1 and M2 to specific values (M1 = 10 and M2 = 0) within the fRK4M2 function, which might override the values passed as arguments. If you intend to use the passed arguments instead, you can remove those assignments from the fRK4M2 function.
Hope this helps.
##### 15 comentariosMostrar 13 comentarios más antiguosOcultar 13 comentarios más antiguos
cindyawati cindyawati el 19 de Jun. de 2023
Ok, I know where I went wrong when I used the 4th order Runge kutta formula. I tried removing the sigmoid function and my program is still running. But the Y-axis for M3 has a negative value and the O and P graphs remain flat. Why?
cindyawati cindyawati el 20 de Jun. de 2023
Hello @Torsten I wanna ask If I use ODE45 for my problem. I must make 5 function (M1,M2, M3,O,and P) for ODE45 in separate file or I make one file include 5 function? Btw I already try solve my code using ODE45 but i get error like this. How to fix it? Thank you
function CM1 = mymode (t,M1)
M1= 10;
M2 = 0;
M3 = 0;
O = 0;
P=0;
delta=50;
K1= 10^-4;
Ko=0.1;
n=3;
Oa=10;
Pa=100;
mu_1=10^-3;
K2=5*10^-4;
K3=10^-3;
gamma=75;
mu_2=10^-3;
mu_3=10^-3;
mu_o=10^-4;
mu_p= 10^-5;
CM1= zeros(2,1);
CM1(1) = (delta*M1*(1-(M1/gamma))-2*K1*M1*M1-M1*(K2*M2)-((Oa-n)*K3*M1*M3)-((Pa-Oa)*Ko*M1*O)-(mu_1*M1));
CM1(2) = (K1*M1*M1)-(K2*M1*M2)-(mu_2*M2);
CM1(3) = (K2*M1*M2)-(K3*M1*M3)-(mu_3*M3);
CM1(4) = (K3*M1*M3)-(Ko*M1*O)-(mu_o*O);
CM1(5) = (Ko*M1*O)-(mu_p*P);
[t,M1] = ode45(mymode, [0,100],[0,1])
plot (t,M1)
end
>> mymode
Out of memory. The likely cause is an infinite recursion within the program.
Error in mymode (line 31)
[t,M1] = ode45(mymode, [0,100],[0,1])

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