In matplotlib, how do you display an axis on both

问题:

I want to draw a plot with matplotlib with axis on both sides of the plot, similar to this plot (the color is irrelevant to this question):

How can I do this with matplotlib?

Note: contrary to what is shown in the example graph, I want the two axis to be exactly the same, and want to show only one graph. Adding the two axis is only to make reading the graph easier.

回答1:

There are a couple of relevant examples in the online documentation:

• Two Scales (seems to do exactly what you're asking for)
• Dual Fahrenheit and Celsius

回答2:

You can use tick_params() (this I did in Jupyter notebook):

import matplotlib.pyplot as plt

bar(range(10), range(10))
tick_params(labeltop=True, labelright=True)

Generates this image:

UPD: added a simple example for subplots. You should use tick_params() with axis object.

This code sets to display only top labels for the top subplot and bottom labels for the bottom subplot (with corresponding ticks):

import matplotlib.pyplot as plt

f, axarr = plt.subplots(2)

axarr[0].bar(range(10), range(10))
axarr[0].tick_params(labelbottom=False, labeltop=True, labelleft=False, labelright=False,
                     bottom=False, top=True, left=False, right=False)

axarr[1].bar(range(10), range(10, 0, -1))
axarr[1].tick_params(labelbottom=True, labeltop=False, labelleft=False, labelright=False,
                     bottom=True, top=False, left=False, right=False)

Looks like this:

回答3:

I've done this previously using the following:

# Create figure and initial axis    
fig, ax0 = plt.subplots()
# Create a duplicate of the original xaxis, giving you an additional axis object
ax1 = ax.twinx()
# Set the limits of the new axis from the original axis limits
ax1.set_ylim(ax0.get_ylim())

This will exactly duplicate the original y-axis.