Center x-axis labels in line plot

Question

I am building a line plot with two lines, one for high temperatures and the other for low temperatures. The x-axis is based on days over one complete year in datetime format

Answer 1

It often makes sense to use dates directly when plotting. So instead of manually setting fixed locations for the labels, one may use matplotlib.dates locators. To position ticks in the middle of the months, one could choose the 15th of the month,

matplotlib.dates.MonthLocator(bymonthday=15)

A full example:

import pandas as pd
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import matplotlib.ticker as mticker
import random

df = pd.DataFrame(random.sample(range(10000),8760),
                  index = pd.date_range(start ='2013-01-01 00:00:00',
                                        end ='2013-12-31 23:30:00',
                                        freq='1H'),
                  columns =['value'])

fig, ax = plt.subplots()
ax.plot(df.index, df['value'])
ax.set_xlim(pd.Timestamp('2013-01-01 00:00:00'), pd.Timestamp('2013-12-31 23:30:00'))

months = mdates.MonthLocator(bymonth =(1,6,12), bymonthday=15 )
allmonths = mdates.MonthLocator()
m_fmt = mdates.DateFormatter('%b')
ax.xaxis.set_major_locator(allmonths)
ax.xaxis.set_minor_locator(months)

ax.xaxis.set_major_formatter(mticker.NullFormatter())
ax.xaxis.set_minor_formatter(m_fmt)
ax.tick_params(axis="x", which="minor", length=0)
plt.show()