在Matlab和Simulink中建模SIR模型

Question

I am trying to model a SIR epidemic model in matlab and simulink. I think I've already done it in matlab but for some reason my simulink model won't work. It just shows straight lines in a scope. This is my function to calculate differential equations.

function dx = sir(t, x)
  dx = [0; 0; 0];
  beta = .5; 
  delta = .3;
    dx(1) = -beta * x(1) * x(2);
    dx(2) = beta * x(1) * x(2) - delta * x(2);
    dx(3) = delta * x(2);
  end

This is my workspace code to show plot and this is mu simulink with yields this strange plot and this is after autoscaling with initial conditions set to S = 7900000 and R = 0 and I = 10

Answer 1

由Product3和Product2块馈入的求和块List of Signals属性应为|+-而不是|-- 。