Choropleth Map

A choropleth map of unemployment rate per county in the US

Method syntax

import altair as alt
from vega_datasets import data

counties = alt.topo_feature(data.us_10m.url, 'counties')
source = data.unemployment.url

alt.Chart(counties).mark_geoshape().encode(
    color='rate:Q'
).transform_lookup(
    lookup='id',
    from_=alt.LookupData(source, 'id', ['rate'])
).project(
    type='albersUsa'
).properties(
    width=500,
    height=300
)

Attribute syntax

import altair as alt
from vega_datasets import data

counties = alt.topo_feature(data.us_10m.url, 'counties')
source = data.unemployment.url

alt.Chart(counties).mark_geoshape().encode(
    color='rate:Q'
).transform_lookup(
    lookup='id',
    from_=alt.LookupData(source, 'id', ['rate'])
).project(
    type='albersUsa'
).properties(
    width=500,
    height=300
)
# No channel encoding options are specified in this chart
# so the code is the same as for the method-based syntax.