Created
March 22, 2020 07:03
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%matplotlib inline | |
import numpy as np | |
from scipy.integrate import odeint | |
import matplotlib.pyplot as plt | |
# Total population, N. | |
N = 1339200000 | |
# Initial number of infected and recovered individuals, I0 and R0. | |
I0, R0 = 296, 23 | |
# Everyone else, S0, is susceptible to infection initially. | |
S0 = N - I0 - R0 | |
# Contact rate, beta, and mean recovery rate, gamma, (in 1/days). | |
beta, gamma = 1.75, 1./8 | |
# Social distancing factor | |
rho = 1.0 | |
# New beta now becomes a multiplicative factor of rho | |
beta = rho*beta | |
# A grid of time points (in days) | |
t = np.linspace(0, 100, 100) | |
# The SIR model differential equations. | |
def deriv(y, t, N, beta, gamma): | |
S, I, R = y | |
dSdt = -beta * S * I / N | |
dIdt = beta * S * I / N - gamma * I | |
dRdt = gamma * I | |
return dSdt, dIdt, dRdt | |
# Initial conditions vector | |
y0 = S0, I0, R0 | |
# Integrate the SIR equations over the time grid, t. | |
ret = odeint(deriv, y0, t, args=(N, beta, gamma)) | |
S, I, R = ret.T | |
# Plot the data on three separate curves for S(t), I(t) and R(t) | |
fig = plt.figure(facecolor='w') | |
ax = fig.add_subplot(111, axisbelow=True) | |
ax.plot(t, S/1000000000, 'b', alpha=0.5, lw=2, label='Susceptible') | |
ax.plot(t, I/1000000000, 'r', alpha=0.5, lw=2, label='Infected') | |
ax.plot(t, R/1000000000, 'g', alpha=0.5, lw=2, label='Recovered with immunity') | |
ax.set_xlabel('Time /days') | |
ax.set_ylabel('Number (100 Crores)') | |
ax.set_ylim(0,1.5) | |
ax.yaxis.set_tick_params(length=0) | |
ax.xaxis.set_tick_params(length=0) | |
ax.grid(b=True, which='major', c='w', lw=2, ls='-') | |
legend = ax.legend() | |
legend.get_frame().set_alpha(0.5) | |
for spine in ('top', 'right', 'bottom', 'left'): | |
ax.spines[spine].set_visible(False) | |
plt.show() |
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