Pythonでガンマ関数のグラフを作る

import numpy as np
import math
import matplotlib.pyplot as plt

N = 10000
x = np.linspace(-5, 5, N)

y = [0] * N

for i in range(1, N):
    y[i] = math.gamma(x[i])

plt.plot(x, y)
plt.grid()
plt.xlim([-5, 5])
plt.ylim([-10, 10])
plt.show()