Demo Parasite Axes

Introduction

In this lab, you will learn how to create a parasite axes using the mpl_toolkits.axes_grid1.parasite_axes.HostAxes and mpl_toolkits.axes_grid1.parasite_axes.ParasiteAxes modules in Matplotlib. The parasite axes shares the x-scale with a host axes, but shows a different scale in y direction.

VM Tips

After the VM startup is done, click the top left corner to switch to the Notebook tab to access Jupyter Notebook for practice.

Sometimes, you may need to wait a few seconds for Jupyter Notebook to finish loading. The validation of operations cannot be automated because of limitations in Jupyter Notebook.

If you face issues during learning, feel free to ask Labby. Provide feedback after the session, and we will promptly resolve the problem for you.

Import necessary libraries

First, we need to import the necessary libraries. In this lab, we will be using matplotlib.pyplot for plotting, mpl_toolkits.axes_grid1.parasite_axes.HostAxes and mpl_toolkits.axes_grid1.parasite_axes.ParasiteAxes for creating a parasite axes.

import matplotlib.pyplot as plt
from mpl_toolkits.axisartist.parasite_axes import HostAxes

Create a figure and add host axes

We create a figure using plt.figure() method and add a host axes using fig.add_axes() method. Host axes shares the x-scale with parasite axes.

fig = plt.figure()
host = fig.add_axes([0.15, 0.1, 0.65, 0.8], axes_class=HostAxes)

Create parasite axes

We create two parasite axes using host.get_aux_axes() method. We set viewlim_mode=None to ensure that the parasite axes share the same x-scale with the host axes. We also set sharex=host to ensure that the x-scale is shared.

par1 = host.get_aux_axes(viewlim_mode=None, sharex=host)
par2 = host.get_aux_axes(viewlim_mode=None, sharex=host)

Hide right y-axis of host axes

We hide the right y-axis of the host axes using host.axis["right"].set_visible(False) method.

host.axis["right"].set_visible(False)

Show right y-axis of parasite axes 1

We show the right y-axis of the first parasite axes using par1.axis["right"].set_visible(True) method. We also set par1.axis["right"].major_ticklabels.set_visible(True) and par1.axis["right"].label.set_visible(True) to show the tick labels and label of the right y-axis.

par1.axis["right"].set_visible(True)
par1.axis["right"].major_ticklabels.set_visible(True)
par1.axis["right"].label.set_visible(True)

Add right y-axis to parasite axes 2

We add a right y-axis to the second parasite axes using par2.axis["right2"] = par2.new_fixed_axis(loc="right", offset=(60, 0)) method.

par2.axis["right2"] = par2.new_fixed_axis(loc="right", offset=(60, 0))

Plot data on all axes

We plot data on all axes using plot() method. We also set labels and limits for all axes using set() method.

p1, = host.plot([0, 1, 2], [0, 1, 2], label="Density")
p2, = par1.plot([0, 1, 2], [0, 3, 2], label="Temperature")
p3, = par2.plot([0, 1, 2], [50, 30, 15], label="Velocity")

host.set(xlim=(0, 2), ylim=(0, 2), xlabel="Distance", ylabel="Density")
par1.set(ylim=(0, 4), ylabel="Temperature")
par2.set(ylim=(1, 65), ylabel="Velocity")

Add legend and axis colors

We add a legend to the host axes using host.legend() method. We also set the color of the left y-axis label of the host axes, the right y-axis label of the first parasite axes, and the right y-axis label of the second parasite axes to match their respective lines using host.axis["left"].label.set_color(p1.get_color()), par1.axis["right"].label.set_color(p2.get_color()), and par2.axis["right2"].label.set_color(p3.get_color()) methods.

host.legend()

host.axis["left"].label.set_color(p1.get_color())
par1.axis["right"].label.set_color(p2.get_color())
par2.axis["right2"].label.set_color(p3.get_color())

Display the plot

We display the plot using plt.show() method.

plt.show()

Summary

In this lab, we learned how to create a parasite axes using mpl_toolkits.axes_grid1.parasite_axes.HostAxes and mpl_toolkits.axes_grid1.parasite_axes.ParasiteAxes modules in Matplotlib. We also learned how to plot data on the parasite axes and share the x-scale with the host axes.