如何在 matplotlib 日期条形图中的某个日期之后为所有条形着色

Question

I have a dataset that consists of datetime.datetime objects in a list called x and a list of ints called y . I'm plotting them like so:

plt.bar(x, y)
plt.show()

How would I go about colouring all the bars after a given date another colour? I know I can get a list of bars by assigning the result of plt.bar(x, y) but I've never messed around with matplotlib beyond making simple plots.

Answer 1

You could make a boolean mask, where you return 0 or 1 depending on if the date is greater than another date. Then use this array to get a list of colors.

import matplotlib.pyplot as plt
import datetime
import numpy as np

base = datetime.datetime.today()

x = [base - datetime.timedelta(days=x) for x in range(10)]
y = np.random.randint(0, 10, 10)

greater = np.greater(x, datetime.datetime(2020, 4, 7)).astype(int)
colors = np.array(['red', 'green'])

plt.bar(x, y, color=colors[greater])

greater looks like this:

Out[9]: array([1, 1, 1, 1, 1, 1, 0, 0, 0, 0])

And colors[greater] looks like this:

array(['green', 'green', 'green', 'green', 'green', 'green', 'red', 'red',
       'red', 'red'], dtype='<U5')