如何更改感兴趣区域中的 pyplot 背景颜色? [英] How to change pyplot background colour in region of interest?

问题描述

我有一个带有日期时间索引的数据框:

I have a dataframe with a datetime index:

            A  B
date            
2020-05-04  0  0
2020-05-05  5  0
2020-05-07  2  0
2020-05-09  2  0
2020-05-18 -5  0
2020-05-19 -1  0
2020-05-20  0  0
2020-05-21  1  0
2020-05-22  0  0
2020-05-23  3  0
2020-05-24  1  1
2020-05-25  0  1
2020-05-26  4  1
2020-05-27  3  1

我想制作一个线图来随着时间的推移跟踪 A 并在 B 的值为 1 时将图的背景着色为红色.我已经实现了此代码来制作图形:

I want to make a lineplot to track A over time and colour the background of the plot red when the values of B are 1. I have implemented this code to make the graph:

from matplotlib import dates as mdates
from matplotlib.colors import ListedColormap
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

cmap = ListedColormap(['white','red'])

ax.plot(data['A'])
ax.set_xlabel('')
plt.xticks(rotation = 30)
ax.xaxis.set_major_formatter(mdates.DateFormatter('%Y-%m-%d'))
ax.pcolorfast(ax.get_xlim(), ax.get_ylim(),
              data['B'].values[np.newaxis],
              cmap = cmap, alpha = 0.4)
plt.axhline(y = 0, color = 'black')
plt.tight_layout()

这给了我这个图表:

但是红色区域错误地从 2020-05-21 而不是 2020-05-24 开始，并且它没有在数据框中的结束日期结束.如何更改我的代码以解决此问题?

But the red region incorrectly starts from 2020-05-21 rather than 2020-05-24 and it doesn't end at the end date in the dataframe. How can I alter my code to fix this?

推荐答案

如果通过 ax.pcolor(data.)更改 ax.pcolorfast(ax.get_xlim()，... ).index ... ... 即可得到所需的内容当前代码的问题是，通过使用 ax.get_xlim()，它会创建一个统一的矩形网格 虽然你的索引不统一(日期丢失)，所以彩色网格不像预期的那样.整个事情是:

If you change ax.pcolorfast(ax.get_xlim(), ... by ax.pcolor(data.index, ... you get what you want. The problem with the current code is that by using ax.get_xlim(), it creates a uniform rectangular grid while your index is not uniform (dates are missing), so the coloredmeshed is not like expected. The whole thing is:

from matplotlib import dates as mdates
from matplotlib.colors import ListedColormap
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

cmap = ListedColormap(['white','red'])

fig = plt.figure()
ax = fig.add_subplot()

ax.plot(data['A'])
ax.set_xlabel('')

plt.xticks(rotation = 30)
ax.xaxis.set_major_formatter(mdates.DateFormatter('%Y-%m-%d'))
#here are the two changes use pcolor
ax.pcolor(data.index, #use data.index to create the proper grid
          ax.get_ylim(),
          data['B'].values[np.newaxis], 
          cmap = cmap, alpha = 0.4, 
          linewidth=0, antialiased=True)
plt.axhline(y = 0, color = 'black')
plt.tight_layout()

然后你得到

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