No handles with labels found to put in legend error after plotting two plots on one chart

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I'm plotting some features month by month and highlighted some of them. Before I added the highlight, the legend can show automatically but now it returns No handles with labels found to put in legend error.

Example data

df = pd.DataFrame(np.random.randn(10, 4), columns=list('ABCD'))
highlight = ['A', 'B']

fig, ax = plt.subplots(figsize=(15, 5))
plt.plot(df.loc[:, ~df.columns.isin(highlight)], c='gray', alpha=0.5) 
plt.plot(df.loc[:, df.columns.isin(highlight)]) 
months = pd.date_range('2019-04-01','2019-08-01', freq='MS').strftime("%Y-%m").tolist()
plt.legend(loc='center left', bbox_to_anchor=(1.0, 0.5))
z = ax.set_xticklabels(months, rotation=45)

enter image description here

I guess plotting two plots on one chart caused this but don't know how to fix it. I don't want to manually specify legends.

pandas matplotlib python
3 Answers

Simply switch the order of your plt.plot() statements and declare your legend items explicitly like this:

df = pd.DataFrame(np.random.randn(10, 4), columns=list('ABCD'))
highlight = ['A', 'B']

fig, ax = plt.subplots(figsize=(15, 5))
plt.plot(df.loc[:, df.columns.isin(highlight)])
plt.plot(df.loc[:, ~df.columns.isin(highlight)], c='gray', alpha=0.5)
months = pd.date_range('2019-04-01','2019-09-01', freq='MS').strftime("%Y-%m").tolist()
plt.legend(list('ABCD'),loc='center left', bbox_to_anchor=(1.0, 0.5))
z = ax.set_xticklabels(months, rotation=45)
plt.show()

enter image description here

user_91620000
  • Use pandas.DataFrame.plot instead of plt.plot
    • This ensures the column headers are correctly assigned as the labels to the correct line
    • It returns a matplotlib.axes.Axes or a numpy.ndarray of them.
  • This example is using pandas v1.2.3
import pandas as pd
import matplotlib.pyplot as plt

ax = df.loc[:, df.columns.isin(highlight)].plot(figsize=(15, 5))
df.loc[:, ~df.columns.isin(highlight)].plot(c='gray', alpha=0.5, ax=ax)

plt.legend(title='column labels', loc='center left', bbox_to_anchor=(1.0, 0.5))
plt.show()

enter image description here

user_77588040

You can get rid of that error by adding a label parameter whenever you plt.plot(...,label=...), same solution at No handles with labels found to put in legend linechart.

When running your code, I get another error in addition, but that is not part of the question and answer here.

No handles with labels found to put in legend. :13: UserWarning: FixedFormatter should only be used together with FixedLocator z = ax.set_xticklabels(months, rotation=45)

I added label='test' and label='test2' as a start.

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

df = pd.DataFrame(np.random.randn(10, 4), columns=list('ABCD'))
highlight = ['A', 'B']

fig, ax = plt.subplots(figsize=(15, 5))
plt.plot(df.loc[:, ~df.columns.isin(highlight)], c='gray', alpha=0.5, label='test')
plt.plot(df.loc[:, df.columns.isin(highlight)], label='test2')
months = pd.date_range('2019-04-01','2019-08-01', freq='MS').strftime("%Y-%m").tolist()
plt.legend(loc='center left', bbox_to_anchor=(1.0, 0.5))
z = ax.set_xticklabels(months, rotation=45)

The error is gone.

What is still left is only the error that was there anyway and which is not linked with the question:

<ipython-input-78-5f152143ed24>:13: UserWarning: FixedFormatter should only be used together with FixedLocator
  z = ax.set_xticklabels(months, rotation=45)
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