Bar Chart with Highlighted Bar

This example shows a basic bar chart with a single bar highlighted.

Method syntax

import altair as alt
from vega_datasets import data

source = data.wheat()

alt.Chart(source).mark_bar().encode(
    x='year:O',
    y="wheat:Q",
    # The highlight will be set on the result of a conditional statement
    color=alt.condition(
        alt.datum.year == 1810,  # If the year is 1810 this test returns True,
        alt.value('orange'),     # which sets the bar orange.
        alt.value('steelblue')   # And if it's not true it sets the bar steelblue.
    )
).properties(width=600)

Attribute syntax

import altair as alt
from vega_datasets import data

source = data.wheat()

alt.Chart(source).mark_bar().encode(
    x='year:O',
    y="wheat:Q",
    # The highlight will be set on the result of a conditional statement
    color=alt.condition(
        alt.datum.year == 1810,  # If the year is 1810 this test returns True,
        alt.value('orange'),     # which sets the bar orange.
        alt.value('steelblue')   # And if it's not true it sets the bar steelblue.
    )
).properties(width=600)
# No channel encoding options are specified in this chart
# so the code is the same as for the method-based syntax.