How to get a legend displayed for Plotly Scattergeo?

Question

I hacked together this code to plot lat and lon coordinates on a map, and the code works pretty darn well, but I can't seem to get the legend displayed, so it's hard to tell what I'm actually looking at.

import pandas as pd
import pandas_bokeh
import matplotlib.pyplot as plt
import pgeocode
import geopandas as gpd
from shapely.geometry import Point
from geopandas import GeoDataFrame
pandas_bokeh.output_notebook()
import plotly.graph_objects as go

nomi = pgeocode.Nominatim('us')

df_melted['Latitude'] = (nomi.query_postal_code(df_melted['my_zip'].tolist()).latitude)
df_melted['Longitude'] = (nomi.query_postal_code(df_melted['my_zip'].tolist()).longitude)


df_melted['colors'] = df_melted['value'].groupby(df_melted['value']).transform('count')
print(df_melted.shape)
print(df_melted.head())

import plotly.express as px
import plotly.graph_objects as go
import pandas as pd

fig = go.Figure(data=go.Scattergeo(
        lon = df_melted['Longitude'],
        lat = df_melted['Latitude'],
        text = df_melted['value'],
        marker_color = df_melted['colors']
        ))

fig.update_layout(
    autosize=False,
    width=1000,
    height=1000,
    title = 'Footprints Compared Based on Lat & Lon Coordinates)',
    geo_scope='usa',
    showlegend=True
    )

fig.update_layout(legend=dict(
    orientation="h",
    yanchor="bottom",
    y=1.02,
    xanchor="right",
    x=1
))
fig.show()

When I run the code, I see a nice map of the US, but there is not legend, even though I'm using this small script directly below, which came straight from the Plotly documentation.

legend=True & showlegend=True

Both gave me errors. Any idea how to get the legend to show up here?

Answer 1

• have used earthquake data to be able to simulate df_melted with compatible columns
• there really is only one missing parameter: marker_coloraxis="coloraxis"
• also changed showlegend=False

full working example using OP plotting code

import pandas as pd
import matplotlib.pyplot as plt
import geopandas as gpd
from shapely.geometry import Point
from geopandas import GeoDataFrame
import plotly.graph_objects as go
import requests

res = requests.get(
    "https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/2.5_week.geojson"
)

us = (
    gpd.read_file(gpd.datasets.get_path("naturalearth_lowres"))
    .loc[lambda d: d["iso_a3"].eq("USA"), "geometry"]
    .values[0]
)
gdf = gpd.GeoDataFrame.from_features(res.json(), crs="epsg:4386").loc[
    lambda d: d.intersects(us)
]
df_melted = pd.DataFrame(
    {
        "Latitude": gdf["geometry"].y,
        "Longitude": gdf["geometry"].x,
        "colors": gdf["mag"],
        "value": gdf["place"],
    }
)
fig = go.Figure(
    data=go.Scattergeo(
        lon=df_melted["Longitude"],
        lat=df_melted["Latitude"],
        text=df_melted["value"],
        marker_color=df_melted["colors"],
        marker_coloraxis="coloraxis",
    )
)

fig.update_layout(
    autosize=False,
    width=400,
    height=400,
    title="Footprints Compared Based on Lat & Lon Coordinates)",
    geo_scope="usa",
    showlegend=False,
)

fig.update_layout(
    legend=dict(orientation="h", yanchor="bottom", y=1.02, xanchor="right", x=1)
)
fig.show()