# 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.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):
s = f'{self:.1f}'
return f'{self:.0f}' if s[-1] == '0' else s

# 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)


Out:

<a list of 7 text.Text objects>


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)


Out:

<a list of 3 text.Text objects>


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:

matplotlib.axes.Axes.contour
matplotlib.pyplot.contour
matplotlib.axes.Axes.clabel
matplotlib.pyplot.clabel
matplotlib.ticker.LogFormatterMathtext
matplotlib.ticker.TickHelper.create_dummy_axis


Out:

<function TickHelper.create_dummy_axis at 0x7f08c0351700>


Total running time of the script: ( 0 minutes 1.322 seconds)

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