如何在 matplotlib 中添加额外的 y 轴标签

Question

I'm trying to add an additional axis label on the right side of an axis, but don't want ticks nor tick labels.

import pandas as pd
import matplotlib.pyplot as plt

fig, axs = plt.subplots(2,2,sharey=True,sharex=True)
for i in range(2):
    for j in range(2):
        pd.Series(np.random.random(10)).plot(ax=axs[i,j])
        axs[0,j].set_title('j = {}'.format(j))
    ax[1,j].set_ylabel('x')
    secaxy = axs[i,1].secondary_yaxis('right')
    secaxy.set_ylabel('i = {}'.format(i))
    secaxy.set_yticks([])
    ax[i,0].set_ylabel('y')

For some reason the set_yticks([]) doesn't replace the ticks.

[In]: secaxy.get_yticks()
[Out:] array([-0.25,  0.  ,  0.25,  0.5 ,  0.75,  1.  ,  1.25])

What would be a convenient way to get an additional axis label on the right side of the plot without ticks?

Answer 1

I wouldn't misuse a secondary axes for that. Just put the label to the right and turn it visible.

import matplotlib.pyplot as plt
import pandas as pd
import numpy as np

fig, axs = plt.subplots(2,2,sharey=True,sharex=True) 
for i in range(2):
    for j in range(2):
        pd.Series(np.random.random(10)).plot(ax=axs[i,j])
for j in range(2):
    axs[0,j].set_title('j = {}'.format(j))
for i in range(2):
    axs[i,1].set_ylabel('i = {}'.format(i))
    axs[i,1].yaxis.get_label().set_visible(True)
    axs[i,1].yaxis.set_label_position("right")
    axs[i,0].set_ylabel('y')

plt.show()