SIR-Model.jl

#SIR-model.jl
# katso https://www.maa.org/press/periodicals/loci/joma/the-sir-model-for-spread-of-disease-the-differential-equation-model

using Plots

function SIR(x,s,i,r,delta_t,n)
    for j in 1 : n-1
        s[j+1] = s[j] - b* s[j]*i[j]*delta_t
        i[j+1] = i[j] + (b*s[j]*i[j] - k*i[j])*delta_t
        r[j+1] = r[j] + k*i[j]*delta_t
    end
    y = [s i r]
    plot(x,y,title = "SIR model",label = ["s" "i" "r"],xlabel="yksikkö päivä", lw= 2)
end

# Alkuarvot
days = 150;
delta_t = 1;
n = div(days,delta_t)
x = Vector(0:delta_t:days-1);
s = zeros(n);
s[1] = 1.0;
i = zeros(n);
i[1] = 1.27e-6;
r = zeros(n);
r[1] = 0.0;
b = 1.0/2;
k = 1.0/3;
# ajo
SIR(x,s,i,r,delta_t,n)