Python中用Plotly绘制等值区域图：能否仅用州名替代州代码？

Great question! The short answer is yes, you can use full state names as the locations parameter input—but you need to adjust your code to tell the visualization library how to match those names to the map data. Here's why your state-name attempt resulted in an empty map, and how to fix it:

Why Two-Letter Codes Work by Default #

Most Python libraries for US state choropleths (like Plotly Express, which is commonly used for this) default to expecting two-letter state codes (e.g., CA, NY) because this is the standard ISO 3166-2:US format. The library's built-in US state map data is pre-linked to these codes, so matching happens automatically.

How to Make Full State Names Work #

To use full state names, you need to do one of two key things:

1. Specify the Correct Location Matching Mode #

If you're using Plotly Express, add the locationmode parameter and set it to match full state names. For example:

import plotly.express as px

# Assume your dataframe has a column called "state_full" with names like "California"
fig = px.choropleth(
    your_dataframe,
    locations="state_full",  # Your column with full state names
    locationmode="USA-states-names",  # Tells Plotly to match full state names
    color="your_metric_column",  # The data you want to visualize
    scope="usa"  # Focuses the map on the US
)
fig.show()

2. Ensure Your State Names Match the Library's Standard #

Double-check that your state names are spelled, capitalized, and formatted exactly as the library expects:

• No typos (e.g., "Califonia" instead of "California")
• Correct spacing (e.g., "New York" not "NewYork")
• Proper capitalization (e.g., "Texas" not "texas")
• Include full names for territories if needed (e.g., "District of Columbia" not "DC")

Fallback: Convert Names to Codes #

If you run into matching issues even with locationmode set, you can convert full state names to two-letter codes using a helper library like us:

import us
import pandas as pd

# Add a new column with two-letter codes to your dataframe
your_dataframe["state_code"] = your_dataframe["state_full"].apply(
    lambda x: us.states.lookup(x).abbr if us.states.lookup(x) else None
)

# Now use the code column for locations
fig = px.choropleth(
    your_dataframe,
    locations="state_code",
    color="your_metric_column",
    scope="usa"
)
fig.show()

Key Takeaway #

You don't have to use two-letter state codes—full names work fine as long as you either specify the right matching mode or ensure your names align with the library's standard data. The empty map you saw was just the library failing to match your full names to its default code-based map data.

内容的提问来源于stack exchange，提问作者praneeth kandula