Horizontal Aggregate Bar Chart

This example is a bar chart showing the distribution of US population by age in the year 2000.

import altair as alt
from altair.expr import datum

from vega_datasets import data
pop = data.population.url

alt.Chart(pop).mark_bar().encode(
    x=alt.X('sum(people):Q', axis=alt.Axis(title='population')),
    y='age:O'
).properties(
    height=300,
    width=300
).transform_filter(
    datum.year == 2000
)