Datetime issue with matplotlib

Question

I'm pulling my hair to display a series with matplotlib.

I'm working with python 2.7. I have a pandas Dataframe with dates. I converted dates to datetime and I'm trying to display a plot without success.

import pandas as pd
import matplotlib.pyplot as plt
from datetime import datetime, date

#I imported df before

type(df)
<class 'pandas.core.frame.DataFrame'>

# The dataframe
AnneeObs  MoisObs  JourObs  NbFluxEntrant
0        2019        8       19            763
1        2019        8        1           1098
...        ...      ...      ...            ...
655      2017       11        1            428
656      2017       11       13           1530

[657 rows x 4 columns]

# To convert dates to datetime
for i in range(0,len(df)):
     df.loc[i,"dateObs"] = date(year=df.iloc[i,0], month=df.iloc[i,1], 
day=df.iloc[i,2])

df['dateObs'] = pd.DatetimeIndex(df['dateObs'])

# To order by dates
df = df.sort_values("dateObs", ascending=True)

df2 = df[["dateObs", "NbFluxEntrant"]]

df2bis = df2.copy()
df2bis = df2bis.set_index('dateObs')

df2bis

# The new dataframe
            NbFluxEntrant
dateObs                  
2017-11-01            428
2017-11-02            931
...                   ...
2019-08-18            243
2019-08-19            763

[657 rows x 1 columns]

# Maybe it's too much...
df2bis.index = pd.to_datetime(df2bis.index)

type(df2bis.index)
<class 'pandas.core.indexes.datetimes.DatetimeIndex'>

# I tried to display it but...
df2bis.plot()

However, it doesn't work :

Fail to execute line 1: df2bis.plot()
ValueError: view limit minimum 0.0 is less than 1 and is an invalid Matplotlib date value. This often happens if you pass a non-datetime value to an axis that has datetime units

I tried others code but nothing good :

df2bis.plot(x="dateObs", y="NbFluxEntrant")
df2bis.plot(x=df2bis.index.values, y="NbFluxEntrant")

Do you have any suggestions ?

Thanks in advance

EDIT : I tried another code that doesn't work :

import matplotlib

dates = matplotlib.dates.date2num(df2bis.index)
dates

array([736634., 736635.,..., 737289., 737290.])

matplotlib.pyplot.plot_date(dates, df2bis["NbFluxEntrant"])

ValueError: view limit minimum 0.0 is less than 1 and is an invalid Matplotlib date value. This often happens if you pass a non-datetime value to an axis that has datetime units

Hmmm...

Answer 1

I faced a similar issue. You could try this:

df2bis.set_index('dateObs', inplace=True)
df2bis.index = pd.to_datetime(df2bis.index)
df2bis.plot()