I used the answer to this question to try and add a vertical line to my time series plot: How do you plot a vertical line on a time series plot in Pandas?

This is my code:

ax = df.plot(figsize=(12,8), logy=True, title='Random Forest Regressor Performance',\
                 color={'price': 'blue', 'count': 'orange', 'pred': 'green'})

ax.axvline(pd.to_datetime('2021-08-23'), color='r', linestyle='--', lw=2)

And this is my data (I set the date (datetime) as an index):

In my case, using this method results in the line being put way out of the actual data. The idea is to put the line to this graph. What I get:

Expected Result:

CodePudding user response：

I assume that pandas does not set the axis format to date time, but converts the date-time values to number and changes the tick labels. Explicitly creating the axis and setting the correct format works.

Following this accepted-answer, the minimal example below shows how to set the date-time format of the axis and add the hline by using a corresponding date-time string.

import matplotlib.pyplot as plt
import pandas as pd

times = pd.date_range('2021-12-07', periods=500, freq='D')
yvalues = range(times.size)

df = pd.DataFrame(yvalues, times)

fig, ax = plt.subplots(1)
fig.autofmt_xdate()
ax.axvline(pd.to_datetime('2023-01-23'), color='r', linestyle='--', lw=2)
ax = df.plot(ax=ax, title='Random Forest Regressor Performance')
plt.show()

Which results in this plot