使用辅助 y 轴时如何标记 y 轴？

Question

I am trying to label both y-axis, one to say "WLL", the other to say "S&P 500". Right now, I can only label the secondary y-axis (S&P 500).

import pandas as pd
from pandas import DataFrame
from matplotlib import pyplot as plt
import pandas.io.data as web
import datetime as dt

start = '2013-01-01'
end = dt.datetime.today()

df = web.DataReader('WLL', 'yahoo', start, end)
sp = web.DataReader('^GSPC', 'yahoo', start, end)

fig, ax1 = plt.subplots()
df['Close'].plot(ax=ax1,color='g',linewidth=1.0)
sp['Close'].plot(secondary_y=True, ax=ax1,color='b',linewidth=1.0)
ax = df['Close'].plot(); sp['Close'].plot(ax=ax, secondary_y=True)

plt.xlabel('xlabel', fontsize=10)
plt.ylabel('ylabel', fontsize=10)

plt.show()

Answer 1

只需在set_ylabel()之前添加 right_ax ， set_ylabel()所示：

ax.right_ax.set_ylabel()

Answer 2

This can be achieved be setting the label before plotting the secondary y-axis .

fig, ax1 = plt.subplots()
df['Close'].plot(ax=ax1, color='g', linewidth=1.0)
sp['Close'].plot(secondary_y=True, ax=ax1, color='b', linewidth=1.0)
ax = df['Close'].plot(); 
ax.set_ylabel('WLL', fontsize=10);
sp['Close'].plot(ax=ax, secondary_y=True);

plt.xlabel('xlabel', fontsize=10)
plt.ylabel('S&P 500', fontsize=10, rotation=-90)