传染病模型matlab代码

以下是基本的传染病模型的MATLAB代码，包括SIR模型和SEIR模型：

SIR模型：

% SIR model
function dy = SIR_model(t,y,beta,gamma)
    dy = zeros(3,1);
    dy(1) = -beta*y(1)*y(2);
    dy(2) = beta*y(1)*y(2) - gamma*y(2);
    dy(3) = gamma*y(2);
end

% initial conditions
N = 1000; % population size
I0 = 1; % initial number of infected
S0 = N - I0; % initial number of susceptible
R0 = 0; % initial number of recovered
y0 = [S0; I0; R0];

% parameters
beta = 0.3; % infection rate
gamma = 0.1; % recovery rate

% time interval
tspan = [0 100];

% solve ODE
[t,y] = ode45(@(t,y)SIR_model(t,y,beta,gamma),tspan,y0);

% plot results
plot(t,y(:,1),'b',t,y(:,2),'r',t,y(:,3),'g')
legend('Susceptible','Infected','Recovered')
xlabel('Time')
ylabel('Population')

SEIR模型：

% SEIR model
function dy = SEIR_model(t,y,beta,sigma,gamma)
    dy = zeros(4,1);
    dy(1) = -beta*y(1)*y(3);
    dy(2) = beta*y(1)*y(3) - sigma*y(2);
    dy(3) = sigma*y(2) - gamma*y(3);
    dy(4) = gamma*y(3);
end

% initial conditions
N = 1000; % population size
E0 = 1; % initial number of exposed
I0 = 0; % initial number of infected
S0 = N - E0 - I0; % initial number of susceptible
R0 = 0; % initial number of recovered
y0 = [S0; E0; I0; R0];

% parameters
beta = 0.3; % infection rate
sigma = 0.1; % incubation rate
gamma = 0.1; % recovery rate

% time interval
tspan = [0 100];

% solve ODE
[t,y] = ode45(@(t,y)SEIR_model(t,y,beta,sigma,gamma),tspan,y0);

% plot results
plot(t,y(:,1),'b',t,y(:,2),'m',t,y(:,3),'r',t,y(:,4),'g')
legend('Susceptible','Exposed','Infected','Recovered')
xlabel('Time')
ylabel('Population')

在以上代码中，SIR模型中，S表示易感者（Susceptible）、I表示感染者（Infected）、R表示康复者（Recovered）；SEIR模型中，S表示易感者、E表示潜伏者（Exposed）、I表示感染者、R表示康复者。在两个模型中，beta表示感染率，gamma表示康复率。在SEIR模型中，sigma表示潜伏率。