Why month x-ticks are labelled wrongly in a datetime index?

I have a dataset of 12 values, with the index being a datetime64 type and I want to plot a bar graph of the data with the x-ticks showing the Month in English. I have used the MonthLocator and DateFormatter functions of matplotlib. These are working for one dataset but not with the other one. The x-ticks months are labelled wrongly. January should be the first index.

Dataset –> full_corr

              corr
timestamp   
2010-01-31  0.367613
2010-02-28  0.178960
2010-03-31  0.217788
2010-04-30  0.146214
2010-05-31  0.201297
2010-06-30  0.609486
2010-07-31  0.659257
2010-08-31  0.397254
2010-09-30  0.729701
2010-10-31  0.916465
2010-11-30  0.533646
2010-12-31  0.893937

Code used –>

plt.bar(full_corr.index, full_corr['corr'], width=10) # some bugs are there
ax = plt.gca()
locator = mdates.MonthLocator()
month_fmt = mdates.DateFormatter('%b')
ax.xaxis.set_major_locator(locator)
ax.xaxis.set_major_formatter(month_fmt)

Output is –> Output Plot

But when I plot the dataframe directly by using df.plot(kind="bar"), the x-ticks are showed properly in the full datetime format.

Answer

The problem is that 2010-01-31 is too near to 2010-02-01. So when you set width to 10, it overlays Feb.

i.stack.imgur.com/EDewS.png

A soution to solve this is to convert 2010-01-31 to 2010-01.

• pd.to_datetime is used to convert series to datetime.
• pd.Series.dt.strftime converts datetime series to a string in our desired format.

import pandas as pd
import datetime as datetime
import matplotlib.pyplot as plt
import matplotlib.dates as mdates

full_corr = pd.read_csv("1.csv")

# Below two lines are same with full_corr['timestamp'] = pd.to_datetime(full_corr['timestamp']).dt.strftime('%Y-%m')
full_corr['timestamp'] = pd.to_datetime(full_corr['timestamp'])
full_corr['timestamp'] = full_corr['timestamp'].apply(lambda x: datetime.datetime.strftime(x, '%Y-%m'))

full_corr['timestamp'] = pd.to_datetime(full_corr['timestamp'])

plt.bar(full_corr['timestamp'], full_corr['corr'], width=10) # some bugs are there
ax = plt.gca()

locator = mdates.MonthLocator()
month_fmt = mdates.DateFormatter('%b')

ax.xaxis.set_major_locator(locator)
ax.xaxis.set_major_formatter(month_fmt)

plt.show()