python - 如何注释箱线图的中位数、四分位数和须线

Question

我有一个 pandas 数据框，其中包含按“帖子类型”分割的 Facebook 帖子数据。数据框称为“Posts_by_type”，它包含点赞数、分享数和帖子类型。有 3 种类型的帖子:赛车、娱乐和促销。

我想在 matplotlib 中创建一个箱线图，显示每种帖子的点赞数。

我的代码有效:

Posts_by_type.boxplot(column='Likes', by='Type', grid=True)

这会产生以下箱线图:

但是，我还想用相应的数值标记箱线图上的中位数和须线。

这在 matplotlib 中可行吗？如果是这样，任何人都可以给我一些关于如何做的指示吗？

Answer 1

同时为框添加值的解决方案。

import random
import string
import matplotlib.pyplot as plt
import pandas as pd
import numpy as np

def get_x_tick_labels(df, grouped_by):
    tmp = df.groupby([grouped_by]).size()
    return ["{0}: {1}".format(k,v) for k, v in tmp.to_dict().items()]

def series_values_as_dict(series_object):
    tmp = series_object.to_dict().values()
    return [y for y in tmp][0]

def generate_dataframe():
    # Create a pandas dataframe...
    _likes = [random.randint(0,300) for _ in range(100)]
    _type = [random.choice(string.ascii_uppercase[:5]) for _ in range(100)]
    _shares = [random.randint(0,100) for _ in range(100)]
    return pd.DataFrame(
        {'Likes': _likes,
         'Type': _type,
         'shares': _shares
        })

def add_values(bp, ax):
    """ This actually adds the numbers to the various points of the boxplots"""
    for element in ['whiskers', 'medians', 'caps']:
        for line in bp[element]:
            # Get the position of the element. y is the label you want
            (x_l, y),(x_r, _) = line.get_xydata()
            # Make sure datapoints exist 
            # (I've been working with intervals, should not be problem for this case)
            if not np.isnan(y): 
                x_line_center = x_l + (x_r - x_l)/2
                y_line_center = y  # Since it's a line and it's horisontal
                # overlay the value:  on the line, from center to right
                ax.text(x_line_center, y_line_center, # Position
                        '%.3f' % y, # Value (3f = 3 decimal float)
                        verticalalignment='center', # Centered vertically with line 
                        fontsize=16, backgroundcolor="white")

posts_by_type = generate_dataframe()


fig, axes = plt.subplots(1, figsize=(20, 10))

bp_series = posts_by_type.boxplot(column='Likes', by='Type', 
                                  grid=True, figsize=(25, 10), 
                                  ax=axes, return_type='dict', labels=labels)
# This should return a dict, but gives me a Series object, soo...
bp_dict = series_values_as_dict(bp_series)
#Now add the values
add_values(bp_dict, axes)
# Set a label on X-axis for each boxplot
labels = get_x_tick_labels(posts_by_type, 'Type')
plt.xticks(range(1, len(labels) + 1), labels)
# Change some other texts on the graphs?
plt.title('Likes per type of post', fontsize=22)
plt.xlabel('Type', fontsize=18)
plt.ylabel('Likes', fontsize=18)
plt.suptitle('This is a pretty graph')
plt.show()