# 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 with custom level formatters

# This custom formatter removes trailing zeros, e.g. "1.0" becomes "1", and
# then adds a percent sign.
def fmt(x):
s = f"{x:.1f}"
if s.endswith("0"):
s = f"{x:.0f}"
return rf"{s} \%" if plt.rcParams["text.usetex"] else f"{s} %"

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

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 0x7f5f3e761e50>


Total running time of the script: ( 0 minutes 1.250 seconds)

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