如何在 matplotlib 图中突出显示周末？

Question

对于一个简单的时间序列：

import pandas as pd
df = pd.DataFrame({'dt':['2020-01-01', '2020-01-02', '2020-01-04', '2020-01-05', '2020-01-06'], 'foo':[1,2, 4,5,6]})
df['dt'] = pd.to_datetime(df.dt)
df['dt_label']= df['dt'].dt.strftime('%Y-%m-%d %a')
df = df.set_index('dt')
#display(df)
df['foo'].plot()
x =plt.xticks(ticks=df.reset_index().dt.values, labels=df.dt_label, rotation=90, horizontalalignment='right')

如何突出显示周末的 x 轴标签？

编辑

Pandas Plots: Separate color for weekends, pretty printing times on x axis

建议：

def highlight_weekends(ax, timeseries):
    d = timeseries.dt
    ranges = timeseries[d.dayofweek >= 5].groupby(d.year * 100 + d.weekofyear).agg(['min', 'max'])
    for i, tmin, tmax in ranges.itertuples():
        ax.axvspan(tmin, tmax, facecolor='orange', edgecolor='none', alpha=0.1)

但应用它与

highlight_weekends(ax, df.reset_index().dt)

不会改变剧情

Answer 1

我已经稍微扩展了您的示例数据，以便我们可以确保我们可以突出显示多个周末实例。

在这个解决方案中，我创建了一个列'weekend'，它是一列布尔值，指示相应的日期是否在周末。

然后我们遍历这些值并调用ax.axvspan

import pandas as pd
import matplotlib.pyplot as plt

# Add a couple of extra dates to sample data
df = pd.DataFrame({'dt': ['2020-01-01',
                          '2020-01-02',
                          '2020-01-04',
                          '2020-01-05',
                          '2020-01-06',
                          '2020-01-07',
                          '2020-01-09',
                          '2020-01-10',
                          '2020-01-11',
                          '2020-01-12']})
# Fill in corresponding observations
df['foo'] = range(df.shape[0])

df['dt'] = pd.to_datetime(df.dt)

df['dt_label']= df['dt'].dt.strftime('%Y-%m-%d %a')

df = df.set_index('dt')

ax = df['foo'].plot()
plt.xticks(ticks=df.reset_index().dt.values, 
           labels=df.dt_label,
           rotation=90,
           horizontalalignment='right')

# Create an extra column which highlights whether or not a date occurs at the weekend
df['weekend'] = df['dt_label'].apply(lambda x: x.endswith(('Sat', 'Sun')))

# Loop over weekend pairs (Saturdays and Sundays), and highlight
for i in range(df['weekend'].sum() // 2):
    ax.axvspan(df[df['weekend']].index[2*i],
               df[df['weekend']].index[2*i+1],
               alpha=0.5)

Answer 2

这是一个使用 fill_between 绘图函数和 x 轴单位的解决方案，以便可以独立于 DatetimeIndex 和数据频率突出显示周末。

x 轴范围用于以天为单位计算绘图所涵盖的时间范围，这是matplotlib dates 使用的单位。然后计算weekends 掩码并将其传递给fill_between 函数的where 参数。掩码作为右排他处理，因此在这种情况下，它们必须包含星期一，以便在星期一 00:00 之前绘制亮点。由于绘制这些高光可能会在周末发生在边界附近时改变 x 轴范围，因此绘制后 x 轴范围将设置回原始值。

请注意，与axvspan 不同，fill_between 函数需要y1 和y2 参数。出于某种原因，使用默认的 y 轴限制会在图框与周末亮点的顶部和底部之间留下一个小间隙。这个问题可以通过在创建绘图后运行ax.set_ylim(*ax.get_ylim()) 来解决。

这是一个基于提供的示例代码并使用类似于 jwalton 提供的答案的扩展数据集的完整示例：

import numpy as np                   # v 1.19.2
import pandas as pd                  # v 1.1.3
import matplotlib.pyplot as plt      # v 3.3.2
import matplotlib.dates as mdates

# Create sample dataset
dt = pd.to_datetime(['2020-01-01', '2020-01-02', '2020-01-04', '2020-01-05',
                     '2020-01-06', '2020-01-07', '2020-01-09', '2020-01-10',
                     '2020-01-11', '2020-01-14'])
df = pd.DataFrame(dict(foo=range(len(dt))), index=dt)

# Draw pandas plot: setting x_compat=True converts the pandas x-axis units to
# matplotlib date units. This is not necessary for this particular example but
# it is necessary for all cases where the dataframe contains a continuous
# DatetimeIndex (for example ones created with pd.date_range) that uses a
# frequency other than daily
ax = df['foo'].plot(x_compat=True, figsize=(6,4), ylabel='foo')
ax.set_ylim(*ax.get_ylim()) # reset y limits to display highlights without gaps

# Highlight weekends based on the x-axis units
xmin, xmax = ax.get_xlim()
days = np.arange(np.floor(xmin), np.ceil(xmax)+2) # range of days in date units
weekends = [(dt.weekday()>=5)|(dt.weekday()==0) for dt in mdates.num2date(days)]
ax.fill_between(days, *ax.get_ylim(), where=weekends, facecolor='k', alpha=.1)
ax.set_xlim(xmin, xmax) # set limits back to default values

# Create and format x tick for each data point
plt.xticks(df.index.values, df.index.strftime('%d\n%a'), rotation=0, ha='center')

plt.title('Weekends are highlighted from SAT 00:00 to MON 00:00', pad=15, size=12);

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您可以在我发布的here 和here 的答案中找到此解决方案的更多示例。