How can I combine the Exposed population and the Susceptible population to make a total population?

Hi I'm new to matlab, any advice would be great! I'm trying to combine my Suceptible population with my Exposed population, so that I can have a total population. I'm not sure how to do this. Here is part of my code.

%initial conditions

S= N-1;

E=0;

I=1;

CI =0;

y0=[S;E;I;CI];

tspan=[0:Cstop]; %simulate for 35 years (1923-1958)

%pars=[beta,alpha,mu,gamma,delta];

[t,y1]=ode45(@SEICI_rhs,tspan,y0,[],pars);

yi=y1(end,:);

tspan=[Cstop:136]; %simulate for 100 years (1958-2058)

pars=[0,alpha,mu,gamma,delta];

[t,y2]=ode45(@SEICI_rhs,tspan,yi,[],pars);

CDeaths=[y1(:,4); y2(2:end,4)]; % The fourth variable entry is cummulative deaths

Deaths=CDeaths(2:end)-CDeaths(1:end-1);

Susceptibles=[y1(2:end,1); y2(2:end,1)];

Expo=[y1(:,2); y2(2:end,2)];

Exposed=Expo(2:end)+Expo(1:end-1);

Infectious=[y1(2:end,3); y2(2:end,3)];

Totpop=

Answer 1

[Abhinaya Kennedy]

Hi Layla,

To calculate the total population at each time step, sum the "Susceptible", "Exposed" (aligned by offsetting by 1 for correct size), and "Infectious" compartments:

Assuming "Susceptibles" and "Exposed" represent the total counts in each compartment over time and assuming "y1" and "y2" include all compartments correctly, use the following code.

Note: This assumes you want to include "Infectious" in the total population calculation. If there are other compartments like "Recovered", you would need to add those as well

TotalPopulation = Susceptibles + Exposed(2:end) + Infectious;

This assumes deaths are accounted for in the compartment "transitions" and doesn't include a "Recovered" compartment. If your model handles deaths differently or includes additional compartments, adjust accordingly.

If you need to include cumulative deaths differently, adjust for that too. For example, if deaths reduce the total population and are not already accounted for:

TotalPopulationAdjusted = TotalPopulation - CDeaths(2:end); % Adjust based on how deaths are tracked

Hope this helps!