练习：阶乘和Gamma函数
Γ函数是阶乘在实数上的推广
import numpy as np
import matplotlib as mpl
import matplotlib.pyplot as plt
from scipy.special import gamma
from scipy.special import factorial
mpl.rcParams['axes.unicode_minus'] = False
mpl.rcParams['font.sans-serif'] = 'SimHei'
if __name__ == '__main__':
N = 5
x = np.linspace(0, N, 50)
y = gamma(x+1)
plt.figure(facecolor='w')
plt.plot(x, y, 'r-', x, y, 'mo', lw=2, ms=7)
z = np.arange(0, N+1)
f = factorial(z, exact=True) # 阶乘
print(f)
plt.plot(z, f, 'go', markersize=9)
plt.grid(b=True)
plt.xlim(-0.1,N+0.1)
plt.ylim(0.5, np.max(y)*1.05)
plt.xlabel('X', fontsize=15)
plt.ylabel('Gamma(X) - 阶乘', fontsize=15)
plt.title('阶乘和Gamma函数', fontsize=16)
plt.show()
