[FIXED] Ticks and Labels on Twin Axes

Issue

How can I set the labels on the extra axes?

The ticks and labels should be the same on all 4 axes. I'm doing something wrong... Thanks!

import matplotlib.pyplot as plt
plt.rcParams['text.usetex'] = True

plt.figure(figsize=(5,5))
f, ax1 = plt.subplots()
ax2 = ax1.twinx()
ax3 = ax1.twiny()
plt.show()

# create reusable ticks and labels
ticks = [0,1/2,3.14159/4,3.14159/2,1]
labels = [r"$0$", r"$\displaystyle\frac{1}{2}$", r"$\displaystyle\frac{\pi}{4}$", r"$\displaystyle\frac{\pi}{2}$", r"$1$"]

# Version 1: twinx() + xaxis.set_ticks()
plt.figure(figsize=(5,5))
f, ax1 = plt.subplots()
ax2 = ax1.twinx()
ax3 = ax1.twiny()
ax1.xaxis.set_ticks(ticks, labels=labels)
ax1.yaxis.set_ticks(ticks, labels=labels)
ax2.xaxis.set_ticks(ticks, labels=labels)
ax3.yaxis.set_ticks(ticks, labels=labels)
plt.show()

# Version 2: twinx() + set_xticklabels)()
plt.figure(figsize=(5,5))
f, ax1 = plt.subplots()
ax2 = ax1.twinx()
ax3 = ax1.twiny()
ax1.set_xticks(ticks)
ax1.set_xticklabels(labels)
ax1.set_yticks(ticks)
ax1.set_yticklabels(labels)
ax2.set_xticks(ticks)
ax2.set_xticklabels(labels)
ax3.set_yticks(ticks)
ax3.set_yticklabels(labels)
plt.show()

Confused: How come ax1 has both xaxis and yaxis, while ax2, ax3 do not appear to?

Solution

A unintuitive solution based on matplotlib.axes.Axes.twinx:

Create a new Axes with an invisible x-axis and an independent y-axis positioned opposite to the original one (i.e. at right).

This means unintuitively (at least for me) you have to switch x/y at the .twin call.

• unintuitively not concerning the general matplotlib twinx functionality, but concerning such a manual ticks and label assignment

• To highlight that a bit more I used ax2_x and ax3_y in the code.

Disclaimer: Not sure if that will break your plot intention when data is added.

• Probably at least you have to take special care with the data assignment to those twin axes - keeping that "axis switch" in mind.
• Also keep that axis switch" in mind when assigning different ticks and labels to the x/y axis.

But for now I think that's the plot you were looking for:

Code:

import matplotlib.pyplot as plt
plt.rcParams['text.usetex'] = True


# create reusable ticks and labels
ticks = [0,1/2,3.14159/4,3.14159/2,1]
labels = [r"$0$", r"$\displaystyle\frac{1}{2}$", r"$\displaystyle\frac{\pi}{4}$", r"$\displaystyle\frac{\pi}{2}$", r"$1$"]



plt.figure(figsize=(5,5))
f, ax1 = plt.subplots()

ax1.xaxis.set_ticks(ticks, labels=labels)
ax1.yaxis.set_ticks(ticks, labels=labels)


ax2_x = ax1.twiny()  # switch
ax3_y = ax1.twinx()  # switch

ax2_x.xaxis.set_ticks(ticks, labels=labels) 
ax3_y.yaxis.set_ticks(ticks, labels=labels)

plt.show()

Or switch the x/yaxis.set_ticks - with the same effect:

• On second thought, I assume that's the preferred way to do it, especially when data comes into play.

ax2_x = ax1.twinx()
ax3_y = ax1.twiny()
    
ax2_x.yaxis.set_ticks(ticks, labels=labels)  # switch
ax3_y.xaxis.set_ticks(ticks, labels=labels)  # switch

---

In case you don't intend to use the twin axis functionality (that means having different data with different scaling assigned to those axis) but 'only' want the ticks and labels on all 4 axis for better plot readability:

Solution based on answer of ImportanceOfBeingErnest with the same plot result:

import matplotlib.pyplot as plt
plt.rcParams['text.usetex'] = True


# create reusable ticks and labels
ticks = [0,1/2,3.14159/4,3.14159/2,1]
labels = [r"$0$", r"$\displaystyle\frac{1}{2}$", r"$\displaystyle\frac{\pi}{4}$", r"$\displaystyle\frac{\pi}{2}$", r"$1$"]


plt.figure(figsize=(5,5))
f, ax1 = plt.subplots()

ax1.xaxis.set_ticks(ticks, labels=labels)
ax1.yaxis.set_ticks(ticks, labels=labels)
ax1.tick_params(axis="x", bottom=True, top=True, labelbottom=True, labeltop=True)
ax1.tick_params(axis="y", left=True, right=True, labelleft=True, labelright=True)

plt.show()

Answered By - MagnusO_O