标记在seaborn中的boxplot与中值

Question

如何用中值标记seaborn图中的每个箱图？

例如

import seaborn as sns
sns.set_style("whitegrid")
tips = sns.load_dataset("tips")
ax = sns.boxplot(x="day", y="total_bill", data=tips)

如何用中位数或平均值标记每个箱图？

Answer 1

当人们包含样本数据集时,我可以说我喜欢它.给你一个健康的+1!

import seaborn as sns, numpy as np

sns.set_style("whitegrid")
tips = sns.load_dataset("tips")
ax = sns.boxplot(x="day", y="total_bill", data=tips)

medians = tips.groupby(['day'])['total_bill'].median().values
median_labels = [str(np.round(s, 2)) for s in medians]

pos = range(len(medians))
for tick,label in zip(pos,ax.get_xticklabels()):
    ax.text(pos[tick], medians[tick] + 0.5, median_labels[tick], 
            horizontalalignment='center', size='x-small', color='w', weight='semibold')

Answer 2

基于 ShikjarDua 的方法，我创建了一个独立于刻度位置工作的版本。这在处理 seaborn 中的分组数据时会派上用场（即，hue=parameter）。此外，我添加了一个“传单检测”，它改变了每个绘制框的线条。

import seaborn as sns
import matplotlib.pyplot as plt
import matplotlib.patheffects as path_effects

def add_median_labels(ax, precision='.1f'):
    lines = ax.get_lines()
    boxes = [c for c in ax.get_children() if type(c).__name__ == 'PathPatch']
    lines_per_box = int(len(lines) / len(boxes))
    for median in lines[4:len(lines):lines_per_box]:
        x, y = (data.mean() for data in median.get_data())
        # choose value depending on horizontal or vertical plot orientation
        value = x if (median.get_xdata()[1] - median.get_xdata()[0]) == 0 else y
        text = ax.text(x, y, f'{value:{precision}}', ha='center', va='center',
                       fontweight='bold', color='white')
        # create median-colored border around white text for contrast
        text.set_path_effects([
            path_effects.Stroke(linewidth=3, foreground=median.get_color()),
            path_effects.Normal(),
        ])

sns.set_style("darkgrid")
tips = sns.load_dataset("tips")
fig, axes = plt.subplots(2, 2, figsize=(10, 10))
for i_fly, show_fliers in enumerate([True, False]):
    for i_data, data_kwargs in enumerate([{'x': 'day', 'y': 'total_bill'},
                                          {'y': 'day', 'x': 'total_bill'}]):
        box_plot = sns.boxplot(ax=axes[i_fly, i_data], **data_kwargs, data=tips,
                               showfliers=show_fliers, hue="sex")
        add_median_labels(box_plot.axes)
        box_plot.axes.set_title((
            f"{['Fliers', 'No fliers'][i_fly]}, "
            f"{['vertical', 'horizontal'][i_data]}"))
plt.show()

Answer 3

这也可以通过从图本身得出中位数而不用专门从数据中计算中位数来实现

box_plot = sns.boxplot(x="day", y="total_bill", data=tips)

ax = box_plot.axes
lines = ax.get_lines()
categories = ax.get_xticks()

for cat in categories:
    # every 4th line at the interval of 6 is median line
    # 0 -> p25 1 -> p75 2 -> lower whisker 3 -> upper whisker 4 -> p50 5 -> upper extreme value
    y = round(lines[4+cat*6].get_ydata()[0],1) 

    ax.text(
        cat, 
        y, 
        f'{y}', 
        ha='center', 
        va='center', 
        fontweight='bold', 
        size=10,
        color='white',
        bbox=dict(facecolor='#445A64'))

box_plot.figure.tight_layout()