2.2

import numpy as np
import pandas as pd
import sympy as sp
sp.init_printing(use_unicode=True)
import matplotlib.pyplot as plt
plt.rcParams['font.sans-serif']=['Times New Roman + SimSun + WFM Sans SC']
plt.rcParams['mathtext.fontset']='cm'

plt.rcParams['axes.unicode_minus']=False
plt.rcParams['figure.dpi'] = 200

plt.rcParams['figure.figsize'] = [4, 3]

plt.rcParams['font.size'] = 12

plt.rcParams['xtick.direction'] = 'in'
plt.rcParams['ytick.direction'] = 'in'
from scipy.special import gamma
x = np.linspace(-5, 3, 1000)
y = gamma(x)
plt.xlabel('x')
plt.ylabel('y')
plt.title(r'$\Gamma(x)=\int_0^{+\infty}{\rm e}^{-t}tt$')
plt.plot(x, y)
plt.show()