Drawing axes with dates using Matplotlib

Use matplotlib Draw axis with date

Source code and reference links

design sketch

Running results

Code

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.dates as mdates

fig, ax = plt.subplots()

""" Generate the data """
beginDate = '2012-01-01'
endDate = '2018-01-01'

#  Converts a date string to a number （ from 1970-01-01 The difference in the number of days counted ）
x = np.arange(mdates.datestr2num(beginDate), mdates.datestr2num(endDate), 15)
y = np.random.randn(len(x))*3+2

data = {}
#  The digital （ The days are different ） Convert to date object  numpy.datetime64
data['date'] = [np.datetime64(int(c), 'D') for c in x]
data['value'] = y
ax.plot('date', 'value', data=data) 
# ax.plot(data['date'], data['value']) #  Equivalent to the previous line 


""" Format the axis """
#  Set major scale ,  Every time 6 One scale per month 
fmt_half_year = mdates.MonthLocator(interval=6)
ax.xaxis.set_major_locator(fmt_half_year)

#  Set the secondary scale , One scale per month 
fmt_month = mdates.MonthLocator() #  The default can be 
ax.xaxis.set_minor_locator(fmt_month)

#  Set up  x  The scale format of the coordinate axis 
ax.xaxis.set_major_formatter(mdates.DateFormatter("%Y-%m"))

#  Set the range of the abscissa axis 
datemin = np.datetime64(data['date'][0], 'Y')
datemax = np.datetime64(data['date'][-1], 'Y') + np.timedelta64(1, 'Y')
ax.set_xlim(datemin, datemax)

#  Set the display format of the scale 
ax.format_xdata = mdates.DateFormatter('%Y-%m')
ax.format_ydata = lambda x : f'$x:.2f$'
ax.grid(True)

""" Automatically adjust the scale string """
#  Automatic adjustment  x  The scale string of the axis （ rotate ） Make each string have enough space without overlapping 
fig.autofmt_xdate() 

plt.show()

The classes used in the code are briefly introduced , You can click to view the specific parameters or usage .

• matplotlib.dates.datestr2num() Convert date to days difference
• numpy.datetime64() The digital （ The days are different ） Convert to date object numpy.datetime64
• matplotlib.dates.MonthLocator() Set the date scale interval
• matplotlib.dates.DateFormatter() Set the date display format
• fig.autofmt_xdate() Automatic axis adjustment , Uncalled strings will overlap

Unadjusted string