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Why my y value went so high, whereas I using small value?

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cindyawati cindyawati
编辑： cindyawati cindyawati 2023-6-15
Ran in:
I am plotting M1 with RK4 function. I am just using small value of constant but the y value went so high
%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
M3=zeros(length(t),1); %empty array for M3
O=zeros(length(t),1); %empty array for O
P=zeros(length(t),1); %empty array for P
for j = 1:length((t))
T(j+1)=T(j)+dt;
M1(j+1)= M1(j)+1./(1+exp(-T(j)));
k1M1= dt*fRK4M1(M2(j),M3(j),O(j),P(j),M1(j));
k2M1= dt*fRK4M1(M2(j)+k1M2/2,M3(j)+k1M3/2,O(j)+k1O/2,P(j)+k1P/2,M1(j)+k1M1/2);
k3M1= dt*fRK4M1(M2(j)+k2M2/2,M3(j)+k2M3/2,O(j)+k2O/2,P(j)+k2P/2,M1(j)+k2M1/2);
k4M1= dt*fRK4M1(M2(j)+k3M2/2,M3(j)+k3M3/2,O(j)+k3O/2,P(j)+k3P/2,M1(j)+k3M1/2);
M1(j+1) = M1(j)+(1/6*(k1M1+(2*k2M1)+(2*k3M1)+k4M1));
end
Unrecognized function or variable 'fRK4M2'.
figure;
plot (T,M1,'r','Linewidth',3)
xlabel('time')
ylabel('M1')
This is my RK function for M1
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;
mu_2=10^-3;
mu_3=10^-3;
mu_o=10^-4;
mu_p= 10^-5;
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 plot
  2 个评论
Image Analyst
Image Analyst 2023-6-15
People may wait to answer until you attach the fRK4M2 variable or function so that they can run your code.
cindyawati cindyawati
cindyawati cindyawati 2023-6-15
function M2 =fRK4M2(M2,M1)
M1=10;
M2=0;
mu_2=10^-3;
K1= 10^-4;
K2=5*10^-4;
K3=10^-3;
M2 = (K1*M1*M1)-(K2*M1*M2)-(mu_2*M2);
This is my FRK4M2 function

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采纳的回答

Steven Lord
Steven Lord 2023-6-15
Look at the way you're calling your function in the loop:
k1M1= dt*fRK4M1(M2(j),M3(j),O(j),P(j),M1(j));
and the way you've defined it:
function M1 =fRK4M1(M1,M2,M3,O,P)
Did you mean for M1 to be the first input argument in the definition but the last in the call? That smells like a bug.
There's also nothing in your code that changes any element of M2, M3, O, or P from their initial values of 0 so you could save time by simply omitting them from the calls (replacing them with 0.)
  1 个评论
cindyawati cindyawati
cindyawati cindyawati 2023-6-15
编辑：cindyawati cindyawati 2023-6-15
Ran in:
It is work for M1, thank you @Steven Lord
k1M1= dt*fRK4M1(M1(j),M2(j),M3(j),O(j),P(j));
Unrecognized function or variable 'dt'.
but i try to M2, M3, P, and O it is doesnt work
k1M2 = dt*fRK4M2(M1(j),M2(j));
function for M2
function M2 =fRK4M2(M1,M2)
M1=10;
M2=0;
mu_2=10^-3;
K1= 10^-4;
K2=5*10^-4;
K3=10^-3;
M2 = (K1*M1*M1)-(K2*M1*M2)-(mu_2*M2);
end
M2, M3, P, and O I want to get like sigmoid graph but I get linear plot for M2,M3,P, and O

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