How to Plot Logarithmic Axes in Matplotlib

Logarithmic axes help visualize data that spans several orders of magnitude by scaling the axes logarithmically instead of linearly. In Matplotlib, you can easily set logarithmic scales for the x-axis, y-axis, or both using simple methods. Let’s explore straightforward ways to apply logarithmic scales in Matplotlib.

Using plt.xscale('log') and plt.yscale('log')

This is the most straightforward methods to set logarithmic scales on the x-axis and y-axis. You first create a plot normally and then explicitly convert each axis to a log scale.

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(0.1, 10, 100)
y = np.exp(x)

plt.plot(x, y)
plt.xscale('log')
plt.yscale('log')
plt.show()

Output:

Explanation: x is a linear space array, y is exponential values. The plot is initially linear, but then both axes are changed to logarithmic scales using plt.xscale and plt.yscale, which helps visualize data spanning multiple orders of magnitude.

Using ax.set_xscale('log') and ax.set_yscale('log')

This method is the object-oriented equivalent of the first and provides more flexibility when working with multiple subplots or complex figures. Instead of using the pyplot state-machine interface, you use the Axes object to set the scale.

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(0.1, 10, 100)
y = np.exp(x)

fig, ax = plt.subplots()
ax.plot(x, y)
ax.set_xscale('log')
ax.set_yscale('log')
plt.show()

Output

Explanation: fig, ax = plt.subplots() creates a figure and axes for plotting. ax.plot(x, y) plots the data as a line graph. ax.set_xscale('log') and ax.set_yscale('log') change the x and y axes to logarithmic scales.

Using plt.loglog()

This method combines plotting and setting both axes to a logarithmic scale in one step. It’s a very concise way to generate plots where both x and y axes are logarithmic.

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(0.1, 10, 100)
y = np.exp(x)

plt.loglog(x, y)
plt.show()

Output

Explanation: plt.loglog(x, y) creates a plot with both x and y axes set to logarithmic scales in one step, plotting the data as a line graph. plt.show() displays the plot.

Using plt.semilogx() or plt.semilogy()

If only one axis requires logarithmic scaling, these functions are ideal. semilogx applies log scale on the x-axis, while semilogy applies it on the y-axis.

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(0.1, 10, 100)
y = np.exp(x)

plt.semilogx(x, y)  # Log x-axis only
plt.show()

Output:

Explanation: plt.semilogx(x, y) plots the data with the x-axis on a logarithmic scale while keeping the y-axis linear. plt.show() displays the resulting plot.