python factorial函数Python 阶乘factorial,python定义阶乘函数

整数的阶乘(factorial)是所有小于及等于该数的正整数的积，0的阶乘为1。即：n!=1×2×3×...×n。

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, 'm*', lw=2)

z = np.arange(0, N+1)

print z

f = factorial(z, exact=True) # 阶乘

print f

plt.plot(z, f, 'go', markersize=8)

plt.grid(b=True)

plt.xlim(-0.1,N+0.1)

plt.ylim(0.5, np.max(y)*1.05)

plt.xlabel(u'X', fontsize=15)

plt.ylabel(u'Gamma(X) - 阶乘', fontsize=15)

plt.title(u'阶乘和Gamma函数', fontsize=16)

plt.show()