A small, complete example of the issue

I am not sure I understand how label generation work in pandas and I've had several problems in the past. I tried to find some documentation without success so here is my pb. I open a ticket here since I was told on gitter it might be a bug but it might just be me misunderstanding

import numpy as np import pandas as pd import matplotlib.pyplot as plt df = pd.DataFrame({ 'A' : 1., 'B' : pd.Timestamp('20130102'), 'C' : pd.Series(1,index=list(range(4)),dtype='float32'), 'D' : np.array([3] * 4,dtype='int32'), 'E' : pd.Categorical(["test","train","test","train"]), 'F' : 'foo' }) fig = plt.figure() axes = fig.gca() g = df.groupby(['B','F']) print("Nb of %d" % len(g)) g.plot.line(ax=axes, legend=True, x="D", y="C" ) plt.show()

Expected Output

I would expect to see only one label per group there is one group but instead I see 2 labels (only one line plotted).
The real example (in a more complex program), I have 2 groups with a multiindex of 3 keys and it generates 6 labels while it plots 2 lines.
Hence it seems there are as many labels as (nb of groups)* (nb of keys in multindex)

Output of pd.show_versions()

pandas: 0.19.0 nose: 1.3.7 pip: 8.1.2 setuptools: 26.1.1 Cython: 0.24.1 numpy: 1.11.1rc1 scipy: None statsmodels: None xarray: None IPython: 5.1.0 sphinx: 1.4.5 patsy: None dateutil: 2.5.3 pytz: 2016.7 blosc: None bottleneck: None tables: None numexpr: 2.5 matplotlib: 1.5.3 openpyxl: None xlrd: None xlwt: None xlsxwriter: 0.7.3 lxml: None bs4: 4.5.1 html5lib: 0.999 httplib2: 0.9.1 apiclient: None sqlalchemy: None pymysql: None psycopg2: None jinja2: 2.8 boto: None pandas_datareader: None