如果你已经在使用NumPy，你可以这样做。

import numpy as np                                                                                                    
import matplotlib.pyplot as plt                                                                                       
                                                                                                                      
# optional, see below
from matplotlib.ticker import MaxNLocator                                                                             

                                                                                                                      
s, i, r = np.genfromtxt("pan.csv", delimiter=',', unpack=True)                                                        
                                                                                                                      
days = np.arange(1, len(s)+1, dtype=int)                                                                              
                                                                                                                      
fig = plt.figure()                                                                                                    
ax = fig.add_subplot()                                                                                                
                                                                                                                      
ax.plot(days, s)                                                                                                      
ax.plot(days, i)                                                                                                      
ax.plot(days, r)                                                                                                      
                                                                                                                      
# This is optional: it will enforce axis ticks to be integers
ax.xaxis.set_major_locator(MaxNLocator(integer=True))                                                                 
                                                                                                                      
plt.show()

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将数据归一化为百分比，并对每组使用绘图函数。

import numpy as np
import matplotlib.pyplot as plt

s = []
i = []
r = []
with open("pan.csv", "r") as f:
lis = [line.split(",") for line in f]
for n in range(1, 121):
    s.append(int(lis[n][0]))
    i.append(float(lis[n][1]))
    r.append(float(lis[n][2]))

s = np.array(s)
i = np.array(i)
r = np.array(r)

s_percentage = s / (s + i + r)
i_percentage = i / (s + i + r)
r_percentage = r / (s + i + r)

fig, ax = plt.subplots()
ax.plot(s_percentage, label='Susceptible')
ax.plot(i_percentage, label='Infectious')
ax.plot(r_percentage, label='Recovered')

ax.set_xlabel('Days')
ax.set_ylabel('Percentage')
ax.set_title('Pandemic Simulation')
ax.legend()

plt.show()

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