Create a legend with pandas and matplotlib.pyplot

Question

This is my first attempt at plotting with python and I'm having problems creating a legend. These are my imports: ``` import matplotlib.pyplot as plt import pandas ``` I load my data like this: ``` data = pandas.read_csv( 'data/output/limits.dat', sep=r"\s+", encoding = 'utf-8' ) ``` and plot it like this: ``` axdata = data.plot( label = '$|U|^{2}$' , x = 'mass', y = 'U2', style = '-s', markeredgecolor = 'none' ) ``` Apparently axdata is now an `AxesSubplot`. Now I want to create a legend as described here like this: ``` plt.legend( (line1), ('label1') ) ``` but I don't know how to extract a `line` object from an `AxesSubplot` `plt.legend()` on its own works, but I only want some of my lines to feature in the legend. Is this the right approach? Is there another command I can use here? EDIT: For example, if I try: ``` plt.legend( [axdata], ['U2']) ``` I get the error: ``` ~/.virtualenvs/science/lib/python3.3/site-packages/matplotlib/legend.py:613: UserWarning: Legend does not support A…

Accepted Answer

I think what you want to do is be able to display a legend for a subset of the lines on your plot. This should do it:

```
df = pd.DataFrame(np.random.randn(400, 4), columns=['one', 'two', 'three', 'four'])
ax1 = df.cumsum().plot()
lines, labels = ax1.get_legend_handles_labels()
ax1.legend(lines[:2], labels[:2], loc='best')  # legend for first two lines only
```

Giving

Create a legend with pandas and matplotlib.pyplot

Solution

Problem