Problem with simulating with SEIR variant

Question

Clement Koh 2020-7-21

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/568254-problem-with-simulating-with-seir-variant

评论： Clement Koh 2020-7-21

I am currently trying to get results for simulating a SEIR variant model but I am not getting any curves for 3 out of 7 of the variables (I, Q and D). I think the problem came in when I implemented xA and xI into the equations. What i was hoping for is that I wanted to let xA and xI to remain a constant (which will be subtracted from the (3) & (4) respectively. But at the same time, should Y(3) and Y(4) be smaller than the value of xA and xI, the constant will change accordingly to be equal to Y(3) and Y(4), as Y(3) and Y(4) should not be a negative number. Lowest value to remain at 0.

Been trying to troubleshoot it but to no avail. Not sure if anyone can provide me with some insights on this too? Thanks alot :)

%SEIAQRD_Main
to = 1;
tf = 365;
tspan = [to:1:tf];
N = 5000000;
y0 = [N-100 0 50 50 0 0 0]; %Initial conditions
[t,Y] = ode45(@SEIAQRD, tspan, y0);
plot(t,Y)
%SEIAQRD_function_file
function dYdt = SEIAQRD(t,Y)
tests_conducted = 2900;
%Input R0 value for simulation
R0 = 2; %Range of 2.0 to 3.5
%Calculating beta(B)
Duration = 11;
B = R0/Duration;
Trans = 0.13;
c = B/Trans;
%Parameters
N = 5703600;
ep = 1/5.2;
gamma = 1/Duration; 
gammaQ = 1/21; 
alpha = 0.5; 
Miu = (30/50000)*100; 
avg_positive = ((74+49+65+75+120+66+106)/7)/2900;
x = tests_conducted*avg_positive; 
xI = (2/3)*x; 
xA = (1/3)*x; 
tau = 1/1; 
%Define equations
%Y(1)=S, Y(2)=E, Y(3)=I, Y(4)=A
%Y(5)=Q, Y(6)=R, Y(7)=D, 
dYdt = zeros(7,1);
lambda = (c*(Y(3)/N)) + (c*(Y(4)/N));
%Susceptible (S)
dYdt(1) = -(lambda*Y(1));
%Exposed (E)
dYdt(2) = (lambda*Y(1))-(ep*Y(2));
%Symptomatic (I)
if xI>Y(3)
    xI1=Y(3);
elseif xI<=Y(3)
    xI1=xI;
end
dYdt(3) = (ep*alpha*Y(2))-(gamma*Y(3))-(xI1*tau);
%Asymptomatic (A)
if xA>Y(4)
    xA1=Y(4);
elseif xA<=Y(4)
        xA1=xA;
end
dYdt(4) = (ep*(1-alpha)*Y(2))-(gamma*Y(4))-(xA1*tau);
%Quarantine (Q)
dYdt(5) = ((xI1+xA1)*tau)-(gammaQ*Y(5))-(Miu*Y(5));
%Recovered (R)
dYdt(6) = (gammaQ*Y(5))+(gamma*Y(4));
%Death (D)
dYdt(7) = Miu*Y(5);
end

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Answer 1

Alan Stevens 2020-7-21

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/568254-problem-with-simulating-with-seir-variant#answer_468777

编辑：Alan Stevens 2020-7-21

在 MATLAB Online 中打开

I get your results for I, Q and D. See them clearly by changing your Main section to;

%SEIAQRD_Main
to = 1;
tf = 365;
tspan = to:tf;
N = 5000000;
y0 = [N-100 0 50 50 0 0 0]; %Initial conditions
[t,Y] = ode45(@SEIAQRD, tspan, y0);
plot(t,Y)
legend('S','E','I','A','Q','R','D')
figure(2)
plot(t,Y(:,3))
legend('I')
figure(3)
plot(t,Y(:,5),t,Y(:,7))
legend('Q','D')