To add a vertical line on a time series plot in Pandas, we can use:

  • plt.axvline(x_position)
  • ax.axvline(x, color='k', linestyle='--')

For horizontal line to be added to Pandas plot use:

  • ax.axhline(6, color="red", linestyle="--")

Steps to plot vertical or horizontal lines

  • Import matplotlib library
  • Create DataFrame with time series data
  • Create the axes object - ax = df.plot()
  • add verticle line
  • add horizontal line
  • add verticle lines based on range of dates
  • add text to the verticle line

More information can be found: DataFrame.plot - secondary_y

Data

Sample time series data to be plot with Pandas

Date Rate
0 2024-12-18 TBD
1 2024-11-07 TBD
2 2024-09-18 TBD
3 2024-07-31 TBD
4 2024-06-12 TBD

Example - add vertical line to Pandas plot

import pandas as pd
import numpy as np

df = pd.DataFrame(index=pd.date_range("2019-07-01", "2019-07-31")) 
df["y"] = np.logspace(0, 1, num=len(df)) 

ax = df.plot()

ax.axhline(6, color="red", linestyle="--")
ax.axvline("2019-07-24", color="red", linestyle="--")

Output

how-to-plot-a-vertical-line-on-a-time-series-plot-in-pandas.png

Example - add vertical line and text to plot

import matplotlib.pyplot as plt
plt.figure(figsize=(30,10))
fig,ax = plt.subplots()

df_fed['Date'] = pd.to_datetime(df_fed['Date'])

df_2023 = df_fed[(df_fed['Date'] > pd.to_datetime('01/01/2022')) & (df_fed['Date'] < pd.to_datetime('01/01/2024'))]

xposition = df_2023['Date']
for i, xc in enumerate(xposition):
    ax.axvline(x=xc, color='r', linestyle='solid')
    plt.text(xc,1.1,df_2023['Rate'].iloc[i],rotation=0)
df.set_index('DateTime')['Rate_'].plot(rot=45, figsize=(30,10), title= 'Is EURUSD expected to rise?')

Output

To find our more about this example please check: How to get currency data in Python?

Add multiple verticle lines

To add mulitple verticle lines to Pandas plot based on list of dates we can use:

year_range = pd.period_range(start='2000-01-01', end='2023-01-01', freq='Y')
year_range = pd.to_datetime(["%s-01-01 %s:00:00" % (y, (6 * h) % 24) for h, y in enumerate(range(2000, 2023, 4)) ])

xposition = [pd.to_datetime('2010-01-01'), pd.to_datetime('2015-12-31')]
xposition = year_range
for xc in xposition:
    ax.axvline(x=xc, color='r', linestyle='solid')

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