# Contour Label Demo¶

Illustrate some of the more advanced things that one can do with contour labels.

import matplotlib
import numpy as np
import matplotlib.cm as cm
import matplotlib.ticker as ticker
import matplotlib.pyplot as plt

Define our surface

delta = 0.025
x = np.arange(-3.0, 3.0, delta)
y = np.arange(-2.0, 2.0, delta)
X, Y = np.meshgrid(x, y)
Z1 = np.exp(-X**2 - Y**2)
Z2 = np.exp(-(X - 1)**2 - (Y - 1)**2)
Z = (Z1 - Z2) * 2

Make contour labels using creative float classes Follows suggestion of Manuel Metz

# Define a class that forces representation of float to look a certain way
# This remove trailing zero so '1.0' becomes '1'

class nf(float):
def __repr__(self):
str = '%.1f' % (self.__float__(),)
if str[-1] == '0':
return '%.0f' % self.__float__()
else:
return '%.1f' % self.__float__()

# Basic contour plot
fig, ax = plt.subplots()
CS = ax.contour(X, Y, Z)

# Recast levels to new class
CS.levels = [nf(val) for val in CS.levels]

# Label levels with specially formatted floats
if plt.rcParams["text.usetex"]:
fmt = r'%r \%%'
else:
fmt = '%r %%'

ax.clabel(CS, CS.levels, inline=True, fmt=fmt, fontsize=10)

Label contours with arbitrary strings using a dictionary

fig1, ax1 = plt.subplots()

# Basic contour plot
CS1 = ax1.contour(X, Y, Z)

fmt = {}
strs = ['first', 'second', 'third', 'fourth', 'fifth', 'sixth', 'seventh']
for l, s in zip(CS1.levels, strs):
fmt[l] = s

# Label every other level using strings
ax1.clabel(CS1, CS1.levels[::2], inline=True, fmt=fmt, fontsize=10)

Use a Formatter

fig2, ax2 = plt.subplots()

CS2 = ax2.contour(X, Y, 100**Z, locator=plt.LogLocator())
fmt = ticker.LogFormatterMathtext()
fmt.create_dummy_axis()
ax2.clabel(CS2, CS2.levels, fmt=fmt)
ax2.set_title("\$100^Z\$")

plt.show()

## References¶

The use of the following functions, methods and classes is shown in this example:

Keywords: matplotlib code example, codex, python plot, pyplot Gallery generated by Sphinx-Gallery