Plotly的add_vline注释垂直居中及添加可交互图例实现问题

实现代码 #

import plotly.express as px
import pandas as pd
import numpy as np

df = pd.DataFrame({'height': [712, 712, 716, 716, 718, np.nan, np.nan, np.nan, np.nan, np.nan],
                   'moisture ': [0.06, 0.19, 0.18, 0.17, 0.18, np.nan, np.nan, np.nan, np.nan, np.nan],
                   'tasks': ['water', None, None, 'prune', None, None, 'position', None, 'prune', None],
                   'weather': [None, 'humid', None, None, 'wet', None, None, None, None, 'hot']}, 
                  index=['2020-01-04', '2020-01-05', '2020-01-06', '2020-01-07', '2020-01-08', '2020-01-09',
                         '2020-01-10', '2020-01-11', '2020-01-12', '2020-01-13'])
# 转换索引为datetime类型，适配Plotly时间轴规则
df.index = pd.to_datetime(df.index)
df.index.name = 'date'

fig = px.line(df, y="height")

# 计算Y轴数值范围，确定注释竖直中点坐标
y_min = df['height'].min()
y_max = df['height'].max()
y_mid = (y_min + y_max) / 2

# 处理tasks对应红色参考线
task_dates = df.loc[~df["tasks"].isna()].index
for i, x in enumerate(task_dates):
    # 用scatter trace绘制垂直线，支持图例交互
    fig.add_scatter(
        x=[x, x],
        y=[y_min, y_max],
        mode='lines',
        line=dict(width=1, dash='dash', color='red'),
        legendgroup='tasks',
        name='任务标记',
        # 仅第一条同类型线显示图例，避免出现重复条目
        showlegend=True if i == 0 else False
    )
    # 添加中点位置注释
    fig.add_annotation(
        x=x,
        y=y_mid,
        text=df.loc[x, 'tasks'],
        showarrow=False,
        bgcolor='white',
        bordercolor='red',
        legendgroup='tasks'
    )

# 处理weather对应蓝色参考线
weather_dates = df.loc[~df["weather"].isna()].index
for i, x in enumerate(weather_dates):
    fig.add_scatter(
        x=[x, x],
        y=[y_min, y_max],
        mode='lines',
        line=dict(width=1, dash='dash', color='blue'),
        legendgroup='weather',
        name='天气标记',
        showlegend=True if i == 0 else False
    )
    fig.add_annotation(
        x=x,
        y=y_mid,
        text=df.loc[x, 'weather'],
        showarrow=False,
        bgcolor='white',
        bordercolor='blue',
        legendgroup='weather'
    )

fig.show()

关键修改说明 #

• 放弃原生add_vline方法：该方法生成的是布局层级的形状，无法绑定图例实现交互隐藏，改用scatter trace绘制垂直线，天然支持图例关联
• 注释固定中点：提前计算Y轴数值的上下限，取平均值作为所有注释的Y坐标，实现所有参考线注释统一居中
• 分组交互：同类型的线和注释绑定相同的legendgroup参数，点击图例对应条目时，同组的所有线和注释会同时隐藏/显示

内容的提问来源于stack exchange，提问作者Diop Chopra