Fix Python – Adding a y-axis label to secondary y-axis in matplotlib

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Question

Asked By – Osmond Bishop

I can add a y label to the left y-axis using plt.ylabel, but how can I add it to the secondary y-axis?

table = sql.read_frame(query,connection)

table[0].plot(color=colors[0],ylim=(0,100))
table[1].plot(secondary_y=True,color=colors[1])
plt.ylabel('$')

Now we will see solution for issue: Adding a y-axis label to secondary y-axis in matplotlib

Answer

The best way is to interact with the axes object directly

import numpy as np
import matplotlib.pyplot as plt
x = np.arange(0, 10, 0.1)
y1 = 0.05 * x**2
y2 = -1 *y1

fig, ax1 = plt.subplots()

ax2 = ax1.twinx()
ax1.plot(x, y1, 'g-')
ax2.plot(x, y2, 'b-')

ax1.set_xlabel('X data')
ax1.set_ylabel('Y1 data', color='g')
ax2.set_ylabel('Y2 data', color='b')

plt.show()

example graph

This question is answered By – Paul H

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