使用pylab绘制时间序列中的垂直线

Question

my main question is how do i plot a vertical line when my x axis represents a datetime series? eg 1st Jan to 12th Jan, 2106

Some things I tried were:

I already have a graph, made from a Dataframe with dates. I need to plot a vertical line at x=somedate.

days = pd.DatetimeIndex(start='2016-01-07', end='2016-01-031', freq='D')
example=pd.DataFrame(np.arange(7,32),index=days)
gp=example.plot()

I tried using

gp.axvline(x=days[0].date())

However, it shows an error that ordinal line >=1. How can i plot?

Answer 1

I update my comment above with some extra code. Following your code:

import numpy as np
import pandas as pd
import datetime as dt

days = pd.DatetimeIndex(start='2016-01-07', end='2016-01-031', freq='D')
example=pd.DataFrame(np.arange(7,32),index=days)
gp=example.plot()

gp.axvline(x=days[0].date())

# And now the interesting part
# I add one day to the previous left xlim
gp.set_xlim(left = days[0].date() - dt.timedelta(days = 1))
gp.figure.canvas.draw()
gp.figure.show()