"""
Display the contours of a function
===================================

An example demoing how to plot the contours of a function, with
additional layout tweeks.

"""

import numpy as np
import matplotlib.pyplot as plt

def f(x,y):
    return (1 - x / 2 + x ** 5 + y ** 3) * np.exp(-x ** 2 - y ** 2)

n = 256
x = np.linspace(-3, 3, n)
y = np.linspace(-3, 3, n)
X, Y = np.meshgrid(x, y)

plt.contourf(X, Y, f(X, Y), 8, alpha=.75, cmap=plt.cm.hot)
C = plt.contour(X, Y, f(X,Y), 8, colors='black', linewidth=.5)
plt.clabel(C, inline=1, fontsize=10)
plt.xticks([])
plt.yticks([])


# Add a title and a box around it
from matplotlib.patches import FancyBboxPatch
ax = plt.gca()
ax.add_patch(FancyBboxPatch((-0.05, .87),
                            width=.66, height=.165, clip_on=False,
                            boxstyle="square,pad=0", zorder=3,
                            facecolor='white', alpha=1.0,
                            transform=plt.gca().transAxes))

plt.text(-0.05, 1.02, " Contour Plot: plt.contour(..)\n",
      horizontalalignment='left',
      verticalalignment='top',
      size='xx-large',
      transform=plt.gca().transAxes)

plt.text(-0.05, 1.01, "\n\n  Draw contour lines and filled contours ",
      horizontalalignment='left',
      verticalalignment='top',
      size='large',
      transform=plt.gca().transAxes)

plt.show()