When working with Python Plotly, it is often necessary to add a caption below a choropleth map. This can provide additional context or information about the data being displayed. In this article, we will explore three different ways to add a caption below a Python Plotly choropleth map.

Option 1: Using Annotations

One way to add a caption below a choropleth map is by using annotations. Annotations allow you to add text or shapes to a Plotly figure at specific coordinates. To add a caption, we can create a new annotation object and specify its position below the map. Here’s an example:

import plotly.graph_objects as go

# Create choropleth map
fig = go.Figure(data=go.Choropleth(...))

# Add caption using annotations
fig.add_annotation(
    x=0.5,
    y=-0.2,
    text="Caption text",
    showarrow=False,
    font=dict(size=12)
)

# Show the figure
fig.show()

This approach allows you to customize the caption’s position, text, and font size. However, it requires manually adjusting the coordinates to ensure the caption is positioned correctly.

Option 2: Using Annotations and Layout

Another way to add a caption below a choropleth map is by combining annotations with the layout object. This approach allows you to specify the position of the caption relative to the entire figure, rather than using specific coordinates. Here’s an example:

import plotly.graph_objects as go

# Create choropleth map
fig = go.Figure(data=go.Choropleth(...))

# Add caption using annotations and layout
fig.update_layout(
    annotations=[
        dict(
            x=0.5,
            y=-0.2,
            xref="paper",
            yref="paper",
            text="Caption text",
            showarrow=False,
            font=dict(size=12)
        )
    ]
)

# Show the figure
fig.show()

This approach provides more flexibility in positioning the caption, as it is relative to the entire figure. It also allows you to easily add multiple annotations or other layout elements.

Option 3: Using Subplots

A third way to add a caption below a choropleth map is by using subplots. Subplots allow you to create multiple plots within a single figure. By creating a subplot with the choropleth map and a separate subplot for the caption, you can position the caption below the map. Here’s an example:

import plotly.graph_objects as go
from plotly.subplots import make_subplots

# Create choropleth map
fig = go.Figure(data=go.Choropleth(...))

# Create subplot for the caption
fig.add_trace(go.Scatter(
    x=[],
    y=[],
    mode="text",
    text=["Caption text"],
    showlegend=False
))

# Create subplots
fig = make_subplots(rows=2, cols=1, shared_xaxes=True, vertical_spacing=0.1)
fig.add_trace(fig.data[0], row=1, col=1)
fig.add_trace(fig.data[1], row=2, col=1)

# Update layout
fig.update_layout(height=600, width=800)

# Show the figure
fig.show()

This approach allows you to have more control over the positioning of the caption, as it is treated as a separate subplot. However, it requires additional code to create and configure the subplots.

After exploring these three options, it is clear that using annotations and layout (Option 2) is the most flexible and convenient way to add a caption below a Python Plotly choropleth map. It provides the ability to easily position the caption relative to the entire figure and allows for customization of the caption’s appearance. Additionally, it requires less code compared to using subplots (Option 3).