How to annotate pandas date-time format in Matplotlib like Plotly?

Question

How to add annotate text example 1st Lockdown, 2nd Lockdown in Matplotlib like Plotly?

Answer 1

Here is an example using ax.annotate, as another answer suggested:

import matplotlib.pyplot as plt
import pandas as pd

dr = pd.date_range('02-01-2020', '07-01-2020', freq='1D')

y = pd.Series(range(len(dr))) ** 2

fig, ax = plt.subplots()
ax.plot(dr, y)

ax.annotate('1st Lockdown',
            xy=(dr[50], y[50]), #annotate the 50th data point; you could select this in a better way
            xycoords='data', #the xy we passed refers to the data
            xytext=(0, 100), #where we put the text relative to the xy
            textcoords='offset points', #what the xytext coordinates mean
            arrowprops=dict(arrowstyle="->"), #style of the arrow
            ha='center') #center the text horizontally

ax.annotate('2nd Lockdown',
            xy=(dr[100], y[100]), xycoords='data',
            xytext=(0, 100), textcoords='offset points',
            arrowprops=dict(arrowstyle="->"), ha='center')

There are lots of options with annotate, so I would look for an example that matches what you want to do and try and follow that.

Annotations seem to be the "smart" way of doing this in matplotlib; you could also just use axvline and text, but you will likely need to add extra formatting to make things look nicer:

import matplotlib.pyplot as plt
import pandas as pd

dr = pd.date_range('02-01-2020', '07-01-2020', freq='1D')

y = pd.Series(range(len(dr))) ** 2

fig, ax = plt.subplots()
ax.plot(dr, y)

ax.axvline(dr[50], ymin=0, ymax=.7, color='gray')
ax.text(dr[50], .7, '1st Lockdown', transform=ax.get_xaxis_transform(), color='gray')