如何为Matplotlib柱状图添加悬停提示以显示时间与温度数据

要给你的柱状图添加鼠标悬停显示时间和温度的功能，你可以利用Matplotlib的事件监听机制，动态更新标注内容。以下是修改后的完整代码：

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

ts = ['25/02/2023 0:00', '25/02/2023 0:01', '25/02/2023 0:02', '25/02/2023 0:03', '25/02/2023 0:04', '25/02/2023 0:05', '25/02/2023 0:06', '25/02/2023 0:07', 
        '25/02/2023 0:08', '25/02/2023 0:09', '25/02/2023 0:10', '25/02/2023 0:11', '25/02/2023 0:12', '25/02/2023 0:13', '25/02/2023 0:14', '25/02/2023 0:15', 
        '25/02/2023 0:16', '25/02/2023 0:17', '25/02/2023 0:18', '25/02/2023 0:19', '25/02/2023 0:20', '25/02/2023 0:21', '25/02/2023 0:22', '25/02/2023 0:23', 
        '25/02/2023 0:24', '25/02/2023 0:25', '25/02/2023 0:26', '25/02/2023 0:27', '25/02/2023 0:28', '25/02/2023 0:29', '25/02/2023 0:30']

temp = ['0', '-21', '20', '30', '-40', '50', '6', '7', '8', '9', '10', '11', '12', '13', '14', 
        '15', '16', '17', '-18', '19', '20', '21', '22', '23', '24', '25', '26', '27', '28', 
        '29', '68']

df = pd.DataFrame(list(zip(ts, temp)),
                  columns = ['ts', 'temp'])
df['temp']=df['temp'].astype(float)
df1 = df.reset_index()
df100 = pd.DataFrame(data=df1)
df100['ts'] = pd.to_datetime(df100['ts'])
df100['ts'] = df100['ts'].dt.strftime('%d-%m--%H:%M')

# 获取绘图的Axes对象
ax = df100.plot.bar(x="ts", y="temp", rot=90, figsize=(12, 6))
plt.subplots_adjust(bottom=0.2)
plt.xlabel("Time")
plt.ylabel("temp")
plt.title('Temperature')

# 创建初始隐藏的标注
annot = ax.annotate("", xy=(0,0), xytext=(20,20), textcoords="offset points",
                    bbox=dict(boxstyle="round", fc="w"),
                    arrowprops=dict(arrowstyle="->"))
annot.set_visible(False)

# 更新标注内容和位置的函数
def update_annot(rect, idx):
    x = rect.get_x() + rect.get_width() / 2
    y = rect.get_y() + rect.get_height()
    annot.xy = (x, y)
    # 获取对应的时间和温度
    time_val = df100['ts'].iloc[idx]
    temp_val = df100['temp'].iloc[idx]
    text = f"时间: {time_val}\n温度: {temp_val}°C"
    annot.set_text(text)
    annot.get_bbox_patch().set_alpha(0.9)

# 鼠标悬停处理函数
def hover(event):
    vis = annot.get_visible()
    if event.inaxes == ax:
        # 获取所有柱子
        rects = ax.patches
        for idx, rect in enumerate(rects):
            if rect.contains(event)[0]:
                update_annot(rect, idx)
                annot.set_visible(True)
                plt.draw()
                return
    if vis:
        annot.set_visible(False)
        plt.draw()

# 鼠标离开处理函数
def hover_off(event):
    annot.set_visible(False)
    plt.draw()

# 绑定事件
fig = plt.gcf()
fig.canvas.mpl_connect("motion_notify_event", hover)
fig.canvas.mpl_connect("axes_leave_event", hover_off)

plt.show(block=True)

关键部分说明： #

• 获取Axes和柱子对象：通过ax = df100.plot.bar(...)拿到绘图的轴对象，再通过ax.patches获取所有柱状图的矩形元素
• 创建标注：annotate生成一个带箭头的悬浮框，初始设为不可见
• 悬停事件处理：hover函数监听鼠标移动，判断鼠标是否在某个柱子上，若是则更新标注的位置和内容并显示；hover_off函数在鼠标离开轴区域时隐藏标注
• 事件绑定：把两个处理函数分别绑定到鼠标移动事件和轴离开事件上

内容的提问来源于stack exchange，提问作者Ashu