Plotting dates on the x-axis with Python s matplotlib

Question

I am trying to plot information against dates  I have a list of dates in the format  01 02 1991    I converted them by doing the following   x   parser parse date  strftime   Y m d      which gives 19910102  Then I tried to use num2date  import matplotlib dates as dates new x   dates num2date x    Plotting   plt plot date new x  other data  fmt  bo   tz None  xdate True    But I get an error  It says  ValueError  year is out of range   Any solutions

User · Answer

I have too low reputation to add comment to @bernie response, with response to @user1506145. I have run in to same issue.

The answer to it is a interval parameter which fixes things up

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

np.random.seed(1)

N = 100
y = np.random.rand(N)

now = dt.datetime.now()
then = now + dt.timedelta(days=100)
days = mdates.drange(now,then,dt.timedelta(days=1))

plt.gca().xaxis.set_major_formatter(mdates.DateFormatter('%Y-%m-%d'))
plt.gca().xaxis.set_major_locator(mdates.DayLocator(interval=5))
plt.plot(days,y)
plt.gcf().autofmt_xdate()
plt.show()

User · Answer

You can do this more simply using plot   instead of plot date       First  convert your strings to instances of Python datetime date   import datetime as dt  dates     01 02 1991   01 03 1991   01 04 1991   x    dt datetime strptime d   m  d  Y   date   for d in dates  y   range len x     many thanks to Kyss Tao for setting me straight here   Then plot   import matplotlib pyplot as plt import matplotlib dates as mdates  plt gca   xaxis set major formatter mdates DateFormatter   m  d  Y    plt gca   xaxis set major locator mdates DayLocator    plt plot x y  plt gcf   autofmt xdate     Result

User · Answer

As  KyssTao has been saying  help dates num2date  says that the x has to be a float giving the number of days since 0001-01-01 plus one  Hence  19910102 is not 2 Jan 1991  because if you counted 19910101 days from 0001-01-01 you d get something in the year 54513 or similar  divide by 365 25  number of days in a year    Use datestr2num instead  see help dates datestr2num     new x   dates datestr2num date    where date is  01 02 1991

[python] Plotting dates on the x-axis with Python's matplotlib

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