如何用Matplotlib绘制三元函数

#!/usr/bin/env python
#coding=GBK
from mpl_toolkits.mplot3d import Axes3D  
from matplotlib import cm  
from matplotlib.ticker import LinearLocator, FormatStrFormatter  
import matplotlib.pyplot as plt  
import numpy as np

fig = plt.figure()
ax = fig.gca(projection='3d')
X = np.arange(-5, 5, 0.1)
Y = np.arange(-5, 5, 0.1)
X, Y = np.meshgrid(X, Y)
R = - X * Y
Z = R / np.e ** (X**2 + Y**2)
surf = ax.plot_surface(X, Y, Z, rstride=1, cstride=1, cmap=cm.jet,
        linewidth=0, antialiased=False)
ax.set_zlim(-1.01, 1.01)

ax.zaxis.set_major_locator(LinearLocator(10))
ax.zaxis.set_major_formatter(FormatStrFormatter('%.02f'))

fig.colorbar(surf, shrink=0.5, aspect=5)

plt.show()

z = -xy / e ^ (x^2 + y ^2)