python plotly: how to display additional label on hover-CodePudding

I have two area subplots and when I hover over the plot, it displays the value of Val_2 and Val_Yellow. The dataframe contains a column called "Diff" that is the difference between Val_2 and Val_Yellow. How can I display Diff and its value in the bottom of the same white hover-box where Val_2 and Val_Yellow are displayed?

Here is the reproducible code:

import numpy as np
import pandas as pd
import plotly.graph_objects as go
from plotly.subplots import make_subplots 

rng = pd.date_range('2022-04-09', periods=20, freq='D')
np.random.seed(42)
first_df = pd.DataFrame({ 'Date': rng, 'Val' : np.random.randn(len(rng))}) 
first_df['Type'] = 'A'

second_df = pd.DataFrame({ 'Date': rng, 'Val' : np.random.randn(len(rng))}) 
second_df['Type'] = 'B'

final_df =  pd.concat([first_df,second_df]).sort_values(by = 'Date')
final_df['Is_Weekend'] = np.where((final_df['Date'].dt.weekday == 5), 1, 0 )

final_df['Val_2'] = final_df['Val'] * 3
final_df['Diff'] = final_df['Val'] - final_df['Val_2']

A_df = final_df[final_df['Type']=='A']
B_df = final_df[final_df['Type']=='B']

fig = make_subplots(rows=2, cols=1,
                    vertical_spacing = 0.05,
                    shared_xaxes=True)
fig.add_trace(go.Scatter(
    x = A_df['Date'], 
    y = A_df['Val'],
    fill=None,
    mode='lines markers',
    line_color='orange', showlegend=True, name = "Val_Yellow"),
            row = 1, col = 1)
fig.add_trace(go.Scatter(
    x =  A_df['Date'], 
    y = A_df['Val_2'],
    fill='tonexty', # fill area
    mode='lines markers', line_color='red', showlegend=False, name ="Val_2"),
            row = 1, col = 1)
fig.update_xaxes(showgrid=False, row=1, col=1)


fig.add_trace(go.Scatter(
    x = B_df['Date'], 
    y = B_df['Val'],
    fill=None,
    mode='lines markers',
    line_color='blue', showlegend=True, name = "Val_Blue"),
            row = 2, col = 1)

fig.add_trace(go.Scatter(
    x =  B_df['Date'], 
    y = B_df['Val_2'],
    fill='tonexty', # fill area
    mode='lines markers', line_color='red', showlegend=True, name ="Val_2"),
            row = 2, col = 1)

fig.update_yaxes(tickprefix = "$")

fig.update_layout(hovermode='x unified', xaxis_range=[A_df['Date'].iloc[0], A_df['Date'].iloc[len(A_df)-1]])

CodePudding user response：

You can use