How to solve problems with ODE in my SIR model?

clc; close all; clear

b = 0.5; % probability of contracting the disease

y = ode45("epidemia", [0 60], [495; 5; 0]);

N = x(1) + x(2) + x(3); % a fixed population for 500 individuals

g = 0.15; % recovery rate

xdot(1) = - b*x(2)*x(1)/N; % Susceptible differential equation

xdot(2) = b*x(2)*x(1)/N - g*x(2); % Infectious differential equation

xdot(3) = g*x(2); % Recovered differential equation

%x0 = [495; 5; 0]; % Initial 495 Susceptible and 5 Infectious

%t = linspace(0, 60, 600); % 60-week duration (600 data points)

plot(t, y);

legend ('Susceptible', 'Infectious', 'Recovered');

function xdot = epidemia(x, t)

xdot = zeros(3, 1);

end

Errors:

Error using feval

Unrecognized function or variable 'epidemia'.

Error in odearguments (line 90)

f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.

Error in ode45 (line 115)

odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

Error in Untitled4 (line 4)

y = ode45("epidemia", [0 60], [495; 5; 0]);

Untitled4 it's a name of my script.

Answer 1

[Alan Stevens]

Replace

y = ode45("epidemia", [0 60], [495; 5; 0]); 

by

y = ode45(@epidemia, [0 60], [495; 5; 0]); 

[Alan Stevens]

Presumably you are also going to put something more than zeros in function epidemia (which should have the arguments in the order t, x rather than x,t)