How to make choropleth maps in Python with Plotly.
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A Choropleth Map is a map composed of colored polygons. It is used to represent spatial variations of a quantity. This page documents how to build outline choropleth maps, but you can also build choropleth tile maps.
Below we show how to create Choropleth Maps using either Plotly Express' px.choropleth
function or the lower-level go.Choropleth
graph object.
Plotly figures made with Plotly Express px.scatter_geo
, px.line_geo
or px.choropleth
functions or containing go.Choropleth
or go.Scattergeo
graph objects have a go.layout.Geo
object which can be used to control the appearance of the base map onto which data is plotted.
Making choropleth maps requires two main types of input:
id
field or some identifying value in properties
; orplotly
: US states and world countries (see below)The GeoJSON data is passed to the geojson
argument, and the data is passed into the color
argument of px.choropleth
(z
if using graph_objects
), in the same order as the IDs are passed into the location
argument.
Note the geojson
attribute can also be the URL to a GeoJSON file, which can speed up map rendering in certain cases.
Plotly Express is the easy-to-use, high-level interface to Plotly, which operates on a variety of types of data and produces easy-to-style figures.
GeoJSON withfeature.id
¶
Here we load a GeoJSON file containing the geometry information for US counties, where feature.id
is a FIPS code.
In [1]:
from urllib.request import urlopen import json with urlopen('https://raw.githubusercontent.com/plotly/datasets/master/geojson-counties-fips.json') as response: counties = json.load(response) counties["features"][0]
Out[1]:
{'type': 'Feature', 'properties': {'GEO_ID': '0500000US01001', 'STATE': '01', 'COUNTY': '001', 'NAME': 'Autauga', 'LSAD': 'County', 'CENSUSAREA': 594.436}, 'geometry': {'type': 'Polygon', 'coordinates': [[[-86.496774, 32.344437], [-86.717897, 32.402814], [-86.814912, 32.340803], [-86.890581, 32.502974], [-86.917595, 32.664169], [-86.71339, 32.661732], [-86.714219, 32.705694], [-86.413116, 32.707386], [-86.411172, 32.409937], [-86.496774, 32.344437]]]}, 'id': '01001'}Data indexed by
id
¶
Here we load unemployment data by county, also indexed by FIPS code.
In [2]:
import pandas as pd df = pd.read_csv("https://raw.githubusercontent.com/plotly/datasets/master/fips-unemp-16.csv", dtype={"fips": str}) df.head()
Out[2]:
fips unemp 0 01001 5.3 1 01003 5.4 2 01005 8.6 3 01007 6.6 4 01009 5.5 Choropleth map using GeoJSON¶Note In this example we set layout.geo.scope
to usa
to automatically configure the map to display USA-centric data in an appropriate projection. See the Geo map configuration documentation for more information on scopes.
In [3]:
from urllib.request import urlopen import json with urlopen('https://raw.githubusercontent.com/plotly/datasets/master/geojson-counties-fips.json') as response: counties = json.load(response) import pandas as pd df = pd.read_csv("https://raw.githubusercontent.com/plotly/datasets/master/fips-unemp-16.csv", dtype={"fips": str}) import plotly.express as px fig = px.choropleth(df, geojson=counties, locations='fips', color='unemp', color_continuous_scale="Viridis", range_color=(0, 12), scope="usa", labels={'unemp':'unemployment rate'} ) fig.update_layout(margin={"r":0,"t":0,"l":0,"b":0}) fig.show()Indexing by GeoJSON Properties¶
If the GeoJSON you are using either does not have an id
field or you wish to use one of the keys in the properties
field, you may use the featureidkey
parameter to specify where to match the values of locations
.
In the following GeoJSON object/data-file pairing, the values of properties.district
match the values of the district
column:
In [4]:
import plotly.express as px df = px.data.election() geojson = px.data.election_geojson() print(df["district"][2]) print(geojson["features"][0]["properties"])
11-Sault-au-Récollet {'district': '11-Sault-au-Récollet'}
To use them together, we set locations
to district
and featureidkey
to "properties.district"
. The color
is set to the number of votes by the candidate named Bergeron.
Note In this example we set layout.geo.visible
to False
to hide the base map and frame, and we set layout.geo.fitbounds
to 'locations'
to automatically zoom the map to show just the area of interest. See the Geo map configuration documentation for more information on projections and bounds.
In [5]:
import plotly.express as px df = px.data.election() geojson = px.data.election_geojson() fig = px.choropleth(df, geojson=geojson, color="Bergeron", locations="district", featureidkey="properties.district", projection="mercator" ) fig.update_geos(fitbounds="locations", visible=False) fig.update_layout(margin={"r":0,"t":0,"l":0,"b":0}) fig.show()Choropleth maps in Dash¶
Dash is the best way to build analytical apps in Python using Plotly figures. To run the app below, run pip install dash
, click "Download" to get the code and run python app.py
.
Get started with the official Dash docs and learn how to effortlessly style & deploy apps like this with Dash Enterprise.
Sign up for Dash Club → Free cheat sheets plus updates from Chris Parmer and Adam Schroeder delivered to your inbox every two months. Includes tips and tricks, community apps, and deep dives into the Dash architecture. Join now.
Discrete Colors¶In addition to continuous colors, we can discretely-color our choropleth maps by setting color
to a non-numerical column, like the name of the winner of an election.
Note In this example we set layout.geo.visible
to False
to hide the base map and frame, and we set layout.geo.fitbounds
to 'locations'
to automatically zoom the map to show just the area of interest. See the Geo map configuration documentation for more information on projections and bounds.
In [7]:
import plotly.express as px df = px.data.election() geojson = px.data.election_geojson() fig = px.choropleth(df, geojson=geojson, color="winner", locations="district", featureidkey="properties.district", projection="mercator", hover_data=["Bergeron", "Coderre", "Joly"] ) fig.update_geos(fitbounds="locations", visible=False) fig.update_layout(margin={"r":0,"t":0,"l":0,"b":0}) fig.show()Using GeoPandas Data Frames¶
px.choropleth
accepts the geometry
of a GeoPandas data frame as the input to geojson
if the geometry
contains polygons.
In [8]:
import plotly.express as px import geopandas as gpd df = px.data.election() geo_df = gpd.GeoDataFrame.from_features( px.data.election_geojson()["features"] ).merge(df, on="district").set_index("district") fig = px.choropleth(geo_df, geojson=geo_df.geometry, locations=geo_df.index, color="Joly", projection="mercator") fig.update_geos(fitbounds="locations", visible=False) fig.show()Using Built-in Country and State Geometries¶
Plotly comes with two built-in geometries which do not require an external GeoJSON file:
In Plotly.py 6.3 and later, the built-in countries geometry is created from the following sources:
In earlier versions of Plotly.py, the built-in countries geometry is based on Natural Earth data only. Plotly includes data from Natural Earth "as-is". This dataset draws boundaries of countries according to de facto status. See the Natural Earth page for more details.
To use the built-in countries geometry, provide locations
as three-letter ISO country codes.
In [9]:
import plotly.express as px df = px.data.gapminder().query("year==2007") fig = px.choropleth(df, locations="iso_alpha", color="lifeExp", # lifeExp is a column of gapminder hover_name="country", # column to add to hover information color_continuous_scale=px.colors.sequential.Plasma) fig.show()
To use the USA States geometry, set locationmode='USA-states'
and provide locations
as two-letter state abbreviations:
In [10]:
import plotly.express as px fig = px.choropleth(locations=["CA", "TX", "NY"], locationmode="USA-states", color=[1,2,3], scope="usa") fig.show()Choropleth Maps with go.Choropleth¶ United States Choropleth Map¶
In [11]:
import plotly.graph_objects as go import pandas as pd df = pd.read_csv('https://raw.githubusercontent.com/plotly/datasets/master/2011_us_ag_exports.csv') fig = go.Figure(data=go.Choropleth( locations=df['code'], # Spatial coordinates z = df['total exports'].astype(float), # Data to be color-coded locationmode = 'USA-states', # set of locations match entries in `locations` colorscale = 'Reds', colorbar_title = "Millions USD", )) fig.update_layout( title_text = '2011 US Agriculture Exports by State', geo_scope='usa', # limite map scope to USA ) fig.show()Customize choropleth chart¶
In [12]:
import plotly.graph_objects as go import pandas as pd df = pd.read_csv('https://raw.githubusercontent.com/plotly/datasets/master/2011_us_ag_exports.csv') for col in df.columns: df[col] = df[col].astype(str) df['text'] = df['state'] + '<br>' + \ 'Beef ' + df['beef'] + ' Dairy ' + df['dairy'] + '<br>' + \ 'Fruits ' + df['total fruits'] + ' Veggies ' + df['total veggies'] + '<br>' + \ 'Wheat ' + df['wheat'] + ' Corn ' + df['corn'] fig = go.Figure(data=go.Choropleth( locations=df['code'], z=df['total exports'].astype(float), locationmode='USA-states', colorscale='Reds', autocolorscale=False, text=df['text'], # hover text marker_line_color='white', # line markers between states colorbar=dict( title=dict( text="Millions USD" ) ) )) fig.update_layout( title_text='2011 US Agriculture Exports by State<br>(Hover for breakdown)', geo = dict( scope='usa', projection=go.layout.geo.Projection(type = 'albers usa'), showlakes=True, # lakes lakecolor='rgb(255, 255, 255)'), ) fig.show()
In [13]:
import plotly.graph_objects as go import pandas as pd df = pd.read_csv('https://raw.githubusercontent.com/plotly/datasets/master/2014_world_gdp_with_codes.csv') fig = go.Figure(data=go.Choropleth( locations = df['CODE'], z = df['GDP (BILLIONS)'], text = df['COUNTRY'], colorscale = 'Blues', autocolorscale=False, reversescale=True, marker_line_color='darkgray', marker_line_width=0.5, colorbar_tickprefix = '$', colorbar_title = 'GDP<br>Billions US$', )) fig.update_layout( title_text='2014 Global GDP', geo=dict( showframe=False, showcoastlines=False, projection_type='equirectangular' ), annotations = [dict( x=0.55, y=0.1, xref='paper', yref='paper', text='Source: <a href="https://www.cia.gov/library/publications/the-world-factbook/fields/2195.html">\ CIA World Factbook</a>', showarrow = False )] ) fig.show()
In [14]:
import plotly.figure_factory as ff import numpy as np import pandas as pd df_sample = pd.read_csv('https://raw.githubusercontent.com/plotly/datasets/master/laucnty16.csv') df_sample['State FIPS Code'] = df_sample['State FIPS Code'].apply(lambda x: str(x).zfill(2)) df_sample['County FIPS Code'] = df_sample['County FIPS Code'].apply(lambda x: str(x).zfill(3)) df_sample['FIPS'] = df_sample['State FIPS Code'] + df_sample['County FIPS Code'] colorscale = ["#f7fbff", "#ebf3fb", "#deebf7", "#d2e3f3", "#c6dbef", "#b3d2e9", "#9ecae1", "#85bcdb", "#6baed6", "#57a0ce", "#4292c6", "#3082be", "#2171b5", "#1361a9", "#08519c", "#0b4083", "#08306b" ] endpts = list(np.linspace(1, 12, len(colorscale) - 1)) fips = df_sample['FIPS'].tolist() values = df_sample['Unemployment Rate (%)'].tolist() fig = ff.create_choropleth( fips=fips, values=values, scope=['usa'], binning_endpoints=endpts, colorscale=colorscale, show_state_data=False, show_hover=True, asp = 2.9, title_text = 'USA by Unemployment %', legend_title = '% unemployed' ) fig.layout.template = None fig.show()
/home/circleci/project/doc/.venv/lib/python3.9/site-packages/plotly/figure_factory/_county_choropleth.py:808: ShapelyDeprecationWarning: The 'type' attribute is deprecated, and will be removed in the future. You can use the 'geom_type' attribute instead. /home/circleci/project/doc/.venv/lib/python3.9/site-packages/plotly/figure_factory/_county_choropleth.py:330: ShapelyDeprecationWarning: The 'type' attribute is deprecated, and will be removed in the future. You can use the 'geom_type' attribute instead. /home/circleci/project/doc/.venv/lib/python3.9/site-packages/plotly/figure_factory/_county_choropleth.py:357: ShapelyDeprecationWarning: The 'type' attribute is deprecated, and will be removed in the future. You can use the 'geom_type' attribute instead. /home/circleci/project/doc/.venv/lib/python3.9/site-packages/plotly/figure_factory/_county_choropleth.py:847: ShapelyDeprecationWarning: The 'type' attribute is deprecated, and will be removed in the future. You can use the 'geom_type' attribute instead. /home/circleci/project/doc/.venv/lib/python3.9/site-packages/plotly/figure_factory/_county_choropleth.py:852: ShapelyDeprecationWarning: The 'type' attribute is deprecated, and will be removed in the future. You can use the 'geom_type' attribute instead.What About Dash?¶
Dash is an open-source framework for building analytical applications, with no Javascript required, and it is tightly integrated with the Plotly graphing library.
Learn about how to install Dash at https://dash.plot.ly/installation.
Everywhere in this page that you see fig.show()
, you can display the same figure in a Dash application by passing it to the figure
argument of the Graph
component from the built-in dash_core_components
package like this:
import plotly.graph_objects as go # or plotly.express as px fig = go.Figure() # or any Plotly Express function e.g. px.bar(...) # fig.add_trace( ... ) # fig.update_layout( ... ) from dash import Dash, dcc, html app = Dash() app.layout = html.Div([ dcc.Graph(figure=fig) ]) app.run(debug=True, use_reloader=False) # Turn off reloader if inside Jupyter
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